J.-m. Broto - Academia.edu (original) (raw)
Papers by J.-m. Broto
physica status solidi (b), 1982
The band structure of Cd3P2 is presented on the basis of Bodnar's model which is extended by ... more The band structure of Cd3P2 is presented on the basis of Bodnar's model which is extended by Wallace in presence of magnetic field. The oscillations of the Fermi level with magnetic field are calculated and it is found that the amplitude of the oscillations in Cd3P2 is larger than in Cd3As2. The effect of the so‐called free‐electron term is included in the calculation of the g‐factor and cyclotron effective mass. The correction due to the free‐electron term in the g‐factor is smaller (gf ≪ 2) than anticipated and depends on energy. Another interesting result of the calculation is that there is linear relationship between cyclotron effective mass and energy.
Physical Review B, 2006
We consider the spin-1/2 antiferromagnetic Heisenberg chain in a staggered magnetic field describ... more We consider the spin-1/2 antiferromagnetic Heisenberg chain in a staggered magnetic field describing materials such as copper benzoate and copper pyrimidine dinitrate. Using the density-matrix renormalization group for transfer matrices (TMRG) we calculate the magnetization of these materials at finite temperature and arbitrary magnetic field. These results are in excellent agreement with experimental data, allowing for a determination of the inhomogeneity parameter c of copper benzoate (c = 0.043) and copper pyrimidine dinitrate (c = 0.11). The TMRG approach can be applied to rather low temperatures yielding singular field and temperature dependences of susceptibilities.
Physica B: Condensed Matter, 1989
The analysis of high magnetic field magnetization of semimagnetic semiconductors provides a direc... more The analysis of high magnetic field magnetization of semimagnetic semiconductors provides a direct determination of the exchange constants between magnetic ions. Supported by a review of the results obtained in pulsed magnetic fields up to 42 T for II1-xMnx and Pb1-xGdxTe SMSC, we emphasize the importance to use a quasi-static magnetic field with the highest possible value.
Journal of Non-Crystalline Solids, 1990
... OF AMORPHOUS Yx-Sil.x ALLOYS NEAR THE METAL-INSULATOR TRANSITION M. SANQUER, R. TOURBOT, B. B... more ... OF AMORPHOUS Yx-Sil.x ALLOYS NEAR THE METAL-INSULATOR TRANSITION M. SANQUER, R. TOURBOT, B. BOUCHER, JM BROTO', H. RAKOTO* Service de ... gives us the minimal value for He and the order of magnitude for spin-orbit scattering in all the sam-ples #I to ...
Physical Review B, 1994
We report an extensive study on the temperature (T) dependence of the upper critical field H, 2 o... more We report an extensive study on the temperature (T) dependence of the upper critical field H, 2 on Bal "K"Bi03single crystals. The H, 2{T}curve shows a reproducible upward curvature at-22 K.
Solid State Phenomena, 2015
We present resistivity measurements of the upper critical field as a function of temperature for ... more We present resistivity measurements of the upper critical field as a function of temperature for Nd2-xCexCuO4+δ/SrTiO3 single crystal films near antiferromagnetic-superconducting phase boundary (x = 0.14) in magnetic fields up to 90kOe at temperatures down to 0.7K. The data are well described by a two-band/two-gap model for a superconductor in the dirty limit.
Physica B: Condensed Matter, 2004
We measured the magnetoresistance of a two-dimensional electron gas in a strongly disordered sili... more We measured the magnetoresistance of a two-dimensional electron gas in a strongly disordered silicon MOSFET system in the presence of a parallel magnetic field up to 40 T. We observe resistance saturation for magnetic fields larger than the calculated magnetic field for fully spin-polarized electron gas. Our experimental results on the magnetoresistance can be quantitatively described by a transport theory taking into account screening and finite width effects in a spin-polarized electron gas.
MRS Proceedings, 1989
ABSTRACTWe recently reported the observation of a very large magnetoresistance in (001)Fe/(001)Cr... more ABSTRACTWe recently reported the observation of a very large magnetoresistance in (001)Fe/(001)Cr superlattices grown by MBE. The magnetoresistance is found to be very large for thin Cr layers. We ascribe this magnetoresistance to a magnetic gate effect.We recently reported the observation of a very large magnetoresistance in (001)Fe/(001)Cr superlattices with thin Cr layers [1]. A large magnetoresitance has also been observed in Fe/Cr/Fe sandwhiches [2]. In both cases, for Cr layers thinner than about 30 Å an antiparallel coupling of the magnetization of neighbor Fe layers is indicated by magnetic, magneto-optic and light scattering measurements [1–3]. It thus turns out that the large magnetoresistance os associated with the change to parallel alignment in an applied field. In this paper, we present new data on the magnetic and transport properties of Fe/Cr superlattics and we concentrate on the discussion of the microscopic origin of the magnetoresistance
Physical Review B, 1998
Monodispersed nanoparticles of cobalt have been prepared by an original method using the decompos... more Monodispersed nanoparticles of cobalt have been prepared by an original method using the decomposition under hydrogen of an organometallic precursor in the presence of a stabilizing polymer. Two colloids ͑Coll-I and Coll-II͒ have been obtained by changing the organometallic concentration in the polymer. Observation by high-resolution transmission electronic microscopy ͑HRTEM͒ showed Co particles well isolated and regularly dispersed in the polymer with a very narrow size distribution centered around 1.5 nm ͑Coll-I͒ and 2 nm ͑Coll-II͒ diameter. These particles are superparamagnetic above the blocking temperature 9 K ͑Coll-I͒ and 13.5 K ͑Coll-II͒. The particle size deduced from the analyses of the magnetic susceptibilities and magnetization curves are consistent with those measured by HRTEM. Magnetization at 5 K seems to saturate in fields up to 5 T leading to an enhanced mean magnetic moment per atom for both samples, where ͗ Co ͘ϭ1.94Ϯ0.05 B for the smallest particles. High-field magnetization measurements, up to 35 T, increases nearly linearly with the applied field. This is equivalent to an increase of the mean magnetic moment with ͗ Co ͘ϭ2.1Ϯ0.1 B at 35 T for the smallest particles. The effective magnetic anisotropies are found to be larger than that of the bulk materials and decrease with increasing particle size. This set of data allows us to conclude that the enhanced magnetization, its increase with applied magnetic field, and the enhanced effective magnetic anisotropy are associated with the large influence of the surface atoms and are more significant with decreasing size.
Physica B: Condensed Matter, 1998
We investigate high-field ferromagnetic resonance of superparamagnetic particles with uniaxial an... more We investigate high-field ferromagnetic resonance of superparamagnetic particles with uniaxial anisotropy. In this case, since the field is large enough to saturate the magnetization, the thermal orientational fluctuations of the magnetic moment of the particle are negligible. Thus, we derive the dynamic susceptibility of the system on the basis of an independent particle model. High-field ferromagnetic resonance has been performed on fine cobalt particles. The analysis of the spectra obtained at different frequencies allows us to estimate the effective magnetic anisotropy, the gyromagnetic ratio, and the transverse relaxation time.
Physical Review B, 1997
The results of magnetization and magnetic-susceptibility measurements on FeSi single crystals are... more The results of magnetization and magnetic-susceptibility measurements on FeSi single crystals are presented. The temperature dependence of the magnetic susceptibility in the range 5-300 K could be explained by contribution from the temperature-dependent parts due to paramagnetic centers and due to the carriers excited thermally in the intrinsic conductivity region. It is shown that the contribution to magnetic susceptibility of FeSi from single-occupied Anderson localized states is negligible. The values of the Curie-Weiss temperatures, an energy gap, as well as density-of-states effective mass were estimated. ͓S0163-1829͑97͒05213-2͔
Physica B: Condensed Matter, 2001
The magnetic properties of the polycrystalline electron-doped manganites Sm \V Ca V MnO have been... more The magnetic properties of the polycrystalline electron-doped manganites Sm \V Ca V MnO have been studied for 1*x*0.67 under high magnetic "elds up to 50 T. H}¹ phase diagrams have been established. Doping the G-type AFM parent compound CaMnO leads to partial FM correlations superimposed on a AFM component. The former phenomena reaches its maximum strength for x"0.88}0.9. For x"0.8 and below, abrupt metamagnetic transitions occur from the AFM ground state to the FM state with large hysteresis between the "rst magnetization and remanence curves. This phenomena corresponds to the melting of the orbital-or charge-ordered phases. At intermediate concentrations close to x"0.85, the magnetization curves exhibit "rst a FM component and then a metamagnetic transition, so that this behavior can thus be viewed as a sum of the two types of previous behaviors, clearly showing the occurrence of phase separation.
Pulsed magnetic fields up to 50 T and neutron-diffraction measurements have been used in a system... more Pulsed magnetic fields up to 50 T and neutron-diffraction measurements have been used in a systematic investigation of the lattice and magnetic factors contributing to the charge-melting transition in L 1/2 Ca 1/2 MnO 3 perovskites (L:Y→La). A detailed study of the H-T phase diagrams is presented. The remarkable rising of the critical fields ͑nonlinear͒ contrasts with the evolution of the transition temperatures. Possible factors determining the evolution observed under field are discussed in the light of the experimental data.
Physical Review B, 2010
Magneto-optical measurements on ruby under high-pressure conditions provided direct determination... more Magneto-optical measurements on ruby under high-pressure conditions provided direct determination of the trigonal crystal field acting at the t 2g orbitals of Cr 3+ in Al 2 O 3 ͑CrO 6 ͒ and its dependence with pressure. The correlation study between the measured trigonal splitting and the trigonal distortion at the Al 3+-substituted site indicates that the trigonal splitting increases with pressure whereas the trigonal distortion slightly reduces. The result is interpreted in terms of an enhancement of the electron-lattice coupling due to trigonal distortion upon reduction in the Al-O bond distance, i.e., the Cr-O bond distance R. The observed variations can be explained on the basis of empirical R dependence of the trigonal crystal field as ␦V tr ϰ R −n with n = 6. It is shown that this exponent does not change when we consider the pressure variation of the local structure around Cr 3+ obtained from ab initio calculations. By the way, we also demonstrate that a methanol-ethanol mixture is a good pressure transmitting medium at cryogenic temperatures.
Thin Solid Films, 2004
We investigated temperature and magnetic field dependences of the magnetization of h-FeSi 2 singl... more We investigated temperature and magnetic field dependences of the magnetization of h-FeSi 2 single crystals in the temperature range of 5-300 K in magnetic fields up to 15 kOe. The temperature dependence of the magnetic susceptibility of the Cr-and Ni-doped sample can be explained by temperature-dependent contributions due to paramagnetic centres and due to the carriers excited thermally in the extrinsic conductivity region. The values of the paramagnetic Curie temperature as well as activation energy of the donor and acceptor levels are estimated.
Solid State Communications, 1993
We have prepared nickel metal fine particles with mean diameters as low as 4 nanometers and we ha... more We have prepared nickel metal fine particles with mean diameters as low as 4 nanometers and we have studied their magnetic properties. A superparamagnetic behaviour is found for the smallest particles even at helium temperature.
Physical Review B, 2008
High-field Zeeman and Paschen-Back effects have been observed in single crystals of ruby submitte... more High-field Zeeman and Paschen-Back effects have been observed in single crystals of ruby submitted to hydrostatic pressure up to 10 GPa. A specific setup with a miniature diamond-anvil cell has been developed to combine high pressure and pulsed magnetic fields and to perform magnetophotoluminescence measurements. Careful analysis of low-temperature ͑4.2 and 77 K͒ photoluminescence spectra with a 56 T magnetic field applied along the c axis allows for the rectification of the assignment of observed emission lines to corresponding Zeeman-split levels. Besides, the intrinsic Zeeman-splitting factors of excited states reveal a linear pressure-induced increase. This enhancement is a signature of an increase in trigonal distortion induced by hydrostatic pressure. Moreover, spectra with magnetic field perpendicular to crystallographic c axis exhibit a Paschen-Back effect reflecting the progressive alignment of Cr 3+ ions spin along the applied field. However, no pressure modification is observed in this compound, contrarily to the Heisenberg-to-Ising spin character pressure-induced transition observed in alexandrite.
physica status solidi (b), 1984
The authors are indebted to Atomic Energy of Canada Limited, the National Research Council of Can... more The authors are indebted to Atomic Energy of Canada Limited, the National Research Council of Canada, and the Nobel Institute of Physics, Stockholm, for the opportunity to assemble the cooperative program which led to the results presented in this paper. The contributions of the technical group of the Electron Physics I. INTRODUCTION T HE Shubnikov-de Haas effect and Azbel-Kaner cyclotron resonance have been used to investigate the electronic band structures of pure Bi and Sb. These are semimetals characterized by low Fermi energies and charge carriers (electrons and holes in equal number) of small momentum. It is plausible, because of the long de Broglie wavelength of the charge carriers at the Fermi energy in Bi, that the local perturbation produced by alloying a small amount of Sb in Bi will not be resolved and the mean free path of the charge carriers will not be substantially decreased. This argument, as well as the results of Esaki and Heer, 1 suggest that it will be feasible to observe the Shubnikov-de Haas effect and cyclotron resonance in dilute Bi-Sb alloys, and to study their electronic band structure by these effects. The present work reports the observation of these effects in a 1% alloy and gives information on the band structure of dilute Bi-Sb alloys. To the best of our knowledge, the Shubnikov-de Haas effect and Azbel-Kaner cyclotron resonance have not been observed in Bi-Sb alloys in the past. Bi and Sb are group V elements and have very similar crystalline structure. X-ray studies 2 have shown that alloying Bi and Sb results in changes in the lattice
Physica C: Superconductivity, 1993
We measured the upper critical field Hc2 on Ba1-chiKchiBiO3 (0.35&amp... more We measured the upper critical field Hc2 on Ba1-chiKchiBiO3 (0.35<chi<0.40) single crystal down to 2 K in pulsed magnetic fields up to 35 T. Resistive transitions in the magnetic field systematically shift as the temperature decreases and the varrho-H curves saturate for high enough magnetic field strength. The initial slope of the upper critical field (dHc2/dT)Tc is -0.5 T/K. As
physica status solidi (b), 1982
The band structure of Cd3P2 is presented on the basis of Bodnar's model which is extended by ... more The band structure of Cd3P2 is presented on the basis of Bodnar's model which is extended by Wallace in presence of magnetic field. The oscillations of the Fermi level with magnetic field are calculated and it is found that the amplitude of the oscillations in Cd3P2 is larger than in Cd3As2. The effect of the so‐called free‐electron term is included in the calculation of the g‐factor and cyclotron effective mass. The correction due to the free‐electron term in the g‐factor is smaller (gf ≪ 2) than anticipated and depends on energy. Another interesting result of the calculation is that there is linear relationship between cyclotron effective mass and energy.
Physical Review B, 2006
We consider the spin-1/2 antiferromagnetic Heisenberg chain in a staggered magnetic field describ... more We consider the spin-1/2 antiferromagnetic Heisenberg chain in a staggered magnetic field describing materials such as copper benzoate and copper pyrimidine dinitrate. Using the density-matrix renormalization group for transfer matrices (TMRG) we calculate the magnetization of these materials at finite temperature and arbitrary magnetic field. These results are in excellent agreement with experimental data, allowing for a determination of the inhomogeneity parameter c of copper benzoate (c = 0.043) and copper pyrimidine dinitrate (c = 0.11). The TMRG approach can be applied to rather low temperatures yielding singular field and temperature dependences of susceptibilities.
Physica B: Condensed Matter, 1989
The analysis of high magnetic field magnetization of semimagnetic semiconductors provides a direc... more The analysis of high magnetic field magnetization of semimagnetic semiconductors provides a direct determination of the exchange constants between magnetic ions. Supported by a review of the results obtained in pulsed magnetic fields up to 42 T for II1-xMnx and Pb1-xGdxTe SMSC, we emphasize the importance to use a quasi-static magnetic field with the highest possible value.
Journal of Non-Crystalline Solids, 1990
... OF AMORPHOUS Yx-Sil.x ALLOYS NEAR THE METAL-INSULATOR TRANSITION M. SANQUER, R. TOURBOT, B. B... more ... OF AMORPHOUS Yx-Sil.x ALLOYS NEAR THE METAL-INSULATOR TRANSITION M. SANQUER, R. TOURBOT, B. BOUCHER, JM BROTO', H. RAKOTO* Service de ... gives us the minimal value for He and the order of magnitude for spin-orbit scattering in all the sam-ples #I to ...
Physical Review B, 1994
We report an extensive study on the temperature (T) dependence of the upper critical field H, 2 o... more We report an extensive study on the temperature (T) dependence of the upper critical field H, 2 on Bal "K"Bi03single crystals. The H, 2{T}curve shows a reproducible upward curvature at-22 K.
Solid State Phenomena, 2015
We present resistivity measurements of the upper critical field as a function of temperature for ... more We present resistivity measurements of the upper critical field as a function of temperature for Nd2-xCexCuO4+δ/SrTiO3 single crystal films near antiferromagnetic-superconducting phase boundary (x = 0.14) in magnetic fields up to 90kOe at temperatures down to 0.7K. The data are well described by a two-band/two-gap model for a superconductor in the dirty limit.
Physica B: Condensed Matter, 2004
We measured the magnetoresistance of a two-dimensional electron gas in a strongly disordered sili... more We measured the magnetoresistance of a two-dimensional electron gas in a strongly disordered silicon MOSFET system in the presence of a parallel magnetic field up to 40 T. We observe resistance saturation for magnetic fields larger than the calculated magnetic field for fully spin-polarized electron gas. Our experimental results on the magnetoresistance can be quantitatively described by a transport theory taking into account screening and finite width effects in a spin-polarized electron gas.
MRS Proceedings, 1989
ABSTRACTWe recently reported the observation of a very large magnetoresistance in (001)Fe/(001)Cr... more ABSTRACTWe recently reported the observation of a very large magnetoresistance in (001)Fe/(001)Cr superlattices grown by MBE. The magnetoresistance is found to be very large for thin Cr layers. We ascribe this magnetoresistance to a magnetic gate effect.We recently reported the observation of a very large magnetoresistance in (001)Fe/(001)Cr superlattices with thin Cr layers [1]. A large magnetoresitance has also been observed in Fe/Cr/Fe sandwhiches [2]. In both cases, for Cr layers thinner than about 30 Å an antiparallel coupling of the magnetization of neighbor Fe layers is indicated by magnetic, magneto-optic and light scattering measurements [1–3]. It thus turns out that the large magnetoresistance os associated with the change to parallel alignment in an applied field. In this paper, we present new data on the magnetic and transport properties of Fe/Cr superlattics and we concentrate on the discussion of the microscopic origin of the magnetoresistance
Physical Review B, 1998
Monodispersed nanoparticles of cobalt have been prepared by an original method using the decompos... more Monodispersed nanoparticles of cobalt have been prepared by an original method using the decomposition under hydrogen of an organometallic precursor in the presence of a stabilizing polymer. Two colloids ͑Coll-I and Coll-II͒ have been obtained by changing the organometallic concentration in the polymer. Observation by high-resolution transmission electronic microscopy ͑HRTEM͒ showed Co particles well isolated and regularly dispersed in the polymer with a very narrow size distribution centered around 1.5 nm ͑Coll-I͒ and 2 nm ͑Coll-II͒ diameter. These particles are superparamagnetic above the blocking temperature 9 K ͑Coll-I͒ and 13.5 K ͑Coll-II͒. The particle size deduced from the analyses of the magnetic susceptibilities and magnetization curves are consistent with those measured by HRTEM. Magnetization at 5 K seems to saturate in fields up to 5 T leading to an enhanced mean magnetic moment per atom for both samples, where ͗ Co ͘ϭ1.94Ϯ0.05 B for the smallest particles. High-field magnetization measurements, up to 35 T, increases nearly linearly with the applied field. This is equivalent to an increase of the mean magnetic moment with ͗ Co ͘ϭ2.1Ϯ0.1 B at 35 T for the smallest particles. The effective magnetic anisotropies are found to be larger than that of the bulk materials and decrease with increasing particle size. This set of data allows us to conclude that the enhanced magnetization, its increase with applied magnetic field, and the enhanced effective magnetic anisotropy are associated with the large influence of the surface atoms and are more significant with decreasing size.
Physica B: Condensed Matter, 1998
We investigate high-field ferromagnetic resonance of superparamagnetic particles with uniaxial an... more We investigate high-field ferromagnetic resonance of superparamagnetic particles with uniaxial anisotropy. In this case, since the field is large enough to saturate the magnetization, the thermal orientational fluctuations of the magnetic moment of the particle are negligible. Thus, we derive the dynamic susceptibility of the system on the basis of an independent particle model. High-field ferromagnetic resonance has been performed on fine cobalt particles. The analysis of the spectra obtained at different frequencies allows us to estimate the effective magnetic anisotropy, the gyromagnetic ratio, and the transverse relaxation time.
Physical Review B, 1997
The results of magnetization and magnetic-susceptibility measurements on FeSi single crystals are... more The results of magnetization and magnetic-susceptibility measurements on FeSi single crystals are presented. The temperature dependence of the magnetic susceptibility in the range 5-300 K could be explained by contribution from the temperature-dependent parts due to paramagnetic centers and due to the carriers excited thermally in the intrinsic conductivity region. It is shown that the contribution to magnetic susceptibility of FeSi from single-occupied Anderson localized states is negligible. The values of the Curie-Weiss temperatures, an energy gap, as well as density-of-states effective mass were estimated. ͓S0163-1829͑97͒05213-2͔
Physica B: Condensed Matter, 2001
The magnetic properties of the polycrystalline electron-doped manganites Sm \V Ca V MnO have been... more The magnetic properties of the polycrystalline electron-doped manganites Sm \V Ca V MnO have been studied for 1*x*0.67 under high magnetic "elds up to 50 T. H}¹ phase diagrams have been established. Doping the G-type AFM parent compound CaMnO leads to partial FM correlations superimposed on a AFM component. The former phenomena reaches its maximum strength for x"0.88}0.9. For x"0.8 and below, abrupt metamagnetic transitions occur from the AFM ground state to the FM state with large hysteresis between the "rst magnetization and remanence curves. This phenomena corresponds to the melting of the orbital-or charge-ordered phases. At intermediate concentrations close to x"0.85, the magnetization curves exhibit "rst a FM component and then a metamagnetic transition, so that this behavior can thus be viewed as a sum of the two types of previous behaviors, clearly showing the occurrence of phase separation.
Pulsed magnetic fields up to 50 T and neutron-diffraction measurements have been used in a system... more Pulsed magnetic fields up to 50 T and neutron-diffraction measurements have been used in a systematic investigation of the lattice and magnetic factors contributing to the charge-melting transition in L 1/2 Ca 1/2 MnO 3 perovskites (L:Y→La). A detailed study of the H-T phase diagrams is presented. The remarkable rising of the critical fields ͑nonlinear͒ contrasts with the evolution of the transition temperatures. Possible factors determining the evolution observed under field are discussed in the light of the experimental data.
Physical Review B, 2010
Magneto-optical measurements on ruby under high-pressure conditions provided direct determination... more Magneto-optical measurements on ruby under high-pressure conditions provided direct determination of the trigonal crystal field acting at the t 2g orbitals of Cr 3+ in Al 2 O 3 ͑CrO 6 ͒ and its dependence with pressure. The correlation study between the measured trigonal splitting and the trigonal distortion at the Al 3+-substituted site indicates that the trigonal splitting increases with pressure whereas the trigonal distortion slightly reduces. The result is interpreted in terms of an enhancement of the electron-lattice coupling due to trigonal distortion upon reduction in the Al-O bond distance, i.e., the Cr-O bond distance R. The observed variations can be explained on the basis of empirical R dependence of the trigonal crystal field as ␦V tr ϰ R −n with n = 6. It is shown that this exponent does not change when we consider the pressure variation of the local structure around Cr 3+ obtained from ab initio calculations. By the way, we also demonstrate that a methanol-ethanol mixture is a good pressure transmitting medium at cryogenic temperatures.
Thin Solid Films, 2004
We investigated temperature and magnetic field dependences of the magnetization of h-FeSi 2 singl... more We investigated temperature and magnetic field dependences of the magnetization of h-FeSi 2 single crystals in the temperature range of 5-300 K in magnetic fields up to 15 kOe. The temperature dependence of the magnetic susceptibility of the Cr-and Ni-doped sample can be explained by temperature-dependent contributions due to paramagnetic centres and due to the carriers excited thermally in the extrinsic conductivity region. The values of the paramagnetic Curie temperature as well as activation energy of the donor and acceptor levels are estimated.
Solid State Communications, 1993
We have prepared nickel metal fine particles with mean diameters as low as 4 nanometers and we ha... more We have prepared nickel metal fine particles with mean diameters as low as 4 nanometers and we have studied their magnetic properties. A superparamagnetic behaviour is found for the smallest particles even at helium temperature.
Physical Review B, 2008
High-field Zeeman and Paschen-Back effects have been observed in single crystals of ruby submitte... more High-field Zeeman and Paschen-Back effects have been observed in single crystals of ruby submitted to hydrostatic pressure up to 10 GPa. A specific setup with a miniature diamond-anvil cell has been developed to combine high pressure and pulsed magnetic fields and to perform magnetophotoluminescence measurements. Careful analysis of low-temperature ͑4.2 and 77 K͒ photoluminescence spectra with a 56 T magnetic field applied along the c axis allows for the rectification of the assignment of observed emission lines to corresponding Zeeman-split levels. Besides, the intrinsic Zeeman-splitting factors of excited states reveal a linear pressure-induced increase. This enhancement is a signature of an increase in trigonal distortion induced by hydrostatic pressure. Moreover, spectra with magnetic field perpendicular to crystallographic c axis exhibit a Paschen-Back effect reflecting the progressive alignment of Cr 3+ ions spin along the applied field. However, no pressure modification is observed in this compound, contrarily to the Heisenberg-to-Ising spin character pressure-induced transition observed in alexandrite.
physica status solidi (b), 1984
The authors are indebted to Atomic Energy of Canada Limited, the National Research Council of Can... more The authors are indebted to Atomic Energy of Canada Limited, the National Research Council of Canada, and the Nobel Institute of Physics, Stockholm, for the opportunity to assemble the cooperative program which led to the results presented in this paper. The contributions of the technical group of the Electron Physics I. INTRODUCTION T HE Shubnikov-de Haas effect and Azbel-Kaner cyclotron resonance have been used to investigate the electronic band structures of pure Bi and Sb. These are semimetals characterized by low Fermi energies and charge carriers (electrons and holes in equal number) of small momentum. It is plausible, because of the long de Broglie wavelength of the charge carriers at the Fermi energy in Bi, that the local perturbation produced by alloying a small amount of Sb in Bi will not be resolved and the mean free path of the charge carriers will not be substantially decreased. This argument, as well as the results of Esaki and Heer, 1 suggest that it will be feasible to observe the Shubnikov-de Haas effect and cyclotron resonance in dilute Bi-Sb alloys, and to study their electronic band structure by these effects. The present work reports the observation of these effects in a 1% alloy and gives information on the band structure of dilute Bi-Sb alloys. To the best of our knowledge, the Shubnikov-de Haas effect and Azbel-Kaner cyclotron resonance have not been observed in Bi-Sb alloys in the past. Bi and Sb are group V elements and have very similar crystalline structure. X-ray studies 2 have shown that alloying Bi and Sb results in changes in the lattice
Physica C: Superconductivity, 1993
We measured the upper critical field Hc2 on Ba1-chiKchiBiO3 (0.35&amp... more We measured the upper critical field Hc2 on Ba1-chiKchiBiO3 (0.35<chi<0.40) single crystal down to 2 K in pulsed magnetic fields up to 35 T. Resistive transitions in the magnetic field systematically shift as the temperature decreases and the varrho-H curves saturate for high enough magnetic field strength. The initial slope of the upper critical field (dHc2/dT)Tc is -0.5 T/K. As