P. Vlaic - Academia.edu (original) (raw)
Papers by P. Vlaic
Journal of Alloys and Compounds, 2015
The structural stability and ground state electronic properties of Fe/AgCl/Fe (0 0 1) junctions w... more The structural stability and ground state electronic properties of Fe/AgCl/Fe (0 0 1) junctions with c(2 Â 2) Fe/AgCl (0 0 1) heterointerfaces are studied by means of ab initio surface Green's function technique for surface and interfaces. The spin-resolved ballistic conductances across Fe/AgCl/Fe (0 0 1) heterojunctions are determined by using Kubo-Landauer approach. Total energy calculations show that sharp Fe/AgCl (0 0 1) interfaces are possible. The interfacial charge transfer is interface sensitive and generates electrostatic interactions that contribute to the stabilization of Fe/AgCl (0 0 1) interfaces. The magnetism of interfacial Fe layers is robust but is responsive to the interfacial structure. The exchange coupling between Fe electrodes across AgCl barriers shows unexpected oscillations with respect to the spacer thickness that may be related in part with the amount of metal induced gap states in AgCl spacers. A powerful D 1 spin filter effect is evidenced across AgCl barriers. Depending on the interface structure, large magnetoresistance ratios, above 3100%, are predicted. Interfacial interdiffusion may affect the magnetoresistive properties. The lower lattice mismatch at c(2 Â 2) Fe/AgCl (0 0 1) interfaces combined with the strong D 1 direct tunnelling across AgCl barriers make Fe/AgCl (0 0 1) interfaces attractive in the context of magnetoelectronics.
Journal of Applied Physics, 2013
Structural, electronic, and magnetic properties of Fe/CaS (001) interfaces and Fe/CaS/Fe (001) he... more Structural, electronic, and magnetic properties of Fe/CaS (001) interfaces and Fe/CaS/Fe (001) heterostructures have been studied by means of a self-consistent Green's function technique for surface and interfaces implemented within the tight-binding linear muffin-tin orbital formalism. Spin dependent transport properties of the Fe/CaS/Fe (001) tunnel junctions with thin and intermediate barriers, in the current-perpendicular-to-plane geometry, have been determined by means of Kubo-Landauer approach implemented within the tight-binding linear muffin-tin orbital formalism. A small charge rearrangement is evidenced at the Fe/CaS (001) interfaces. The iron interfacial magnetic moments are enhanced over the bulk value. A small exchange coupling with the sign depending on the Fe/CaS (001) interface geometric structure and the strength decaying exponentially with the barrier is evidenced. Interfacial charge transfer, interface iron magnetic moments, and tunneling currents are sensitive to the interfacial structure. Interface resonant states have a decisive role in the tunneling process and the main contribution to the current in the ferromagnetic state of the junction is given by the minority-spin electrons. V C 2013 American Institute of Physics.
The pressure dependences of crystal structures and magnetic properties of YCo5 and GdCo5 compound... more The pressure dependences of crystal structures and magnetic properties of YCo5 and GdCo5 compounds are analysed based on band structure calculations. Isomorphic transitions were evidenced for relative volumes v/v0 = 0.91 and 0.86, for YCo5 and GdCo5, respectively. At the transition, there is a higher decrease of cobalt moments at 3g sites as compared to those located in 2c ones. The induced polarizations on Y4d and Gd5d bands, by short range interactions, are linearly dependent on the magnetizations of cobalt atoms situated in their neighborhood. The isomorphic transitions are analysed in correlations with band structures.
Surface Science, 2004
ABSTRACT The electronic structure and magnetic properties of Fe/GaAs/Fe (001) tunnel junction hav... more ABSTRACT The electronic structure and magnetic properties of Fe/GaAs/Fe (001) tunnel junction have been studied using a first-principles Green's function technique, based on the tight-binding linear muffin-tin orbital method in its atomic spheres approximation, in conjunction with the coherent potential approximation to describe the disorder effects such as the interdiffusion at the interface. The results show that at the Fe/GaAs interface there is a charge transfer from iron to the semiconductor region and an enhancement of Fe magnetic moment. The magnetic properties are found to be sensitive to the interface terminations and influenced by the interdiffusion. The spin dependent transport properties are also discussed.
physica status solidi (c), 2006
Journal of Magnetism and Magnetic Materials, 2002
The Y3Co11−xMxB4 compounds with M=Cu or Al, for x⩽3, crystallize in a hexagonal structure having ... more The Y3Co11−xMxB4 compounds with M=Cu or Al, for x⩽3, crystallize in a hexagonal structure having P6/mmm space group. The compounds are ferromagnetically ordered for x⩽3 (M=Cu) and x<2 (M=Al). The cobalt magnetic moments are very sensitive to exchange interactions. The results of band structure calculations were correlated with those obtained from magnetic measurements.
Journal of Applied Physics, 2004
The electronic structure and magnetic properties of semi-infinite Cu (001)/M/Cu/M/semi-infinite C... more The electronic structure and magnetic properties of semi-infinite Cu (001)/M/Cu/M/semi-infinite Cu (001) multilayer systems with M=Fe, Co, or Ni have been studied by means of a first-principle Green's function technique based on the tight-binding linear muffin-tin orbital method. The results show that at the M/Cu (M=Fe or Co) interfaces there is a net charge transfer from iron and cobalt atoms
Journal of Applied Physics, 2011
The magnetic and transport properties of Fe-Pd/Rh(Ir)/Fe-Pd heterostructures have been analyzed b... more The magnetic and transport properties of Fe-Pd/Rh(Ir)/Fe-Pd heterostructures have been analyzed by means of a first principles Green's technique for surfaces and interfaces, implemented within tight-binding linear muffin-tin method. The effects of variable thicknesses both for spacers and magnetic layers on the magnetic and transport properties were analyzed. The spin-dependent transport properties are determined in the ballistic limit by means of linear response of Kubo approach implemented within tight-binding linear muffin-tin orbital formalism. A correlation between the interlayer exchange coupling, conductances, giant magnetoresistances and magnetic properties are shown. The magnetic disorder, simulating the effect of temperature on the interlayer exchange coupling and transport properties, are also discussed.
Journal of Alloys and Compounds, 2014
Neutron diffraction measurements were performed on HoCo 2 in the pressure range p 6 4.8 GPa. The ... more Neutron diffraction measurements were performed on HoCo 2 in the pressure range p 6 4.8 GPa. The evolutions with pressure of holmium and cobalt moments were correlated with those obtained from band structure calculations. Magnetic properties of Ho x Y 1Àx Co 2 compounds with x 6 0.3 were also investigated in a large temperature range. The magnetic behaviour of cobalt in the above system has been analysed in spin fluctuations model.
Journal of Alloys and Compounds, 2013
ABSTRACT The crystal structure and magnetic properties of TbCo2 compound have been analyzed by ne... more ABSTRACT The crystal structure and magnetic properties of TbCo2 compound have been analyzed by neutron diffraction, at pressures up to 4.1 GPa in the temperature range 10–300 K. A rhombohedral type structure of type is shown below Curie temperature. The distortion degree of structure increases with pressure as well as when lowering temperature. The temperature dependences of terbium and cobalt moments can be described by Brillouin functions. The Curie temperatures decrease linearly with pressure with a slope of dTc/dP = −9 K/GPa. The evolution with pressure of the cobalt magnetic moments and Tb5d band polarizations are theoretically analyzed. The experimental data are well described by band structure calculations. The magnetic behavior of cobalt in heavy rare-earth RCo2 compounds is analyzed in spin fluctuations model. A gradual quenching of spin fluctuations by internal field was shown.
Journal of Alloys and Compounds, 2014
Structural, electronic and spin-dependent transport properties of Fe/NaCl/Fe (0 0 1) tunnel junct... more Structural, electronic and spin-dependent transport properties of Fe/NaCl/Fe (0 0 1) tunnel junctions with c(2 Â 2) structure are studied by means of first-principles calculations. Several Fe/NaCl (0 0 1) interfaces are considered and their stability is analyzed. The interfacial charge transfer has an important role in stabilizing Fe/NaCl (0 0 1) interfaces. Interfacial iron magnetic moments are enhanced over the bulk value. Fe induced gap states are observed in barrier layers on both Na and Cl ions. Small exchange couplings with exponential decays as function of the barriers thickness are evidenced. Resonant tunnelling plays a major role on the spin-polarized transport properties. High magnetoresistance ratios comparable to Fe/MgO/Fe junctions are predicted. Total energy calculations show that interfacial interdiffusion is not favourable but the disorder at interfaces may strongly affect the electronic transport properties. Absence of interfacial interdiffusion together with the small lattice mismatch between Fe and NaCl layers are important advantages of Fe/NaCl/Fe (0 0 1) junctions for the purpose of spintronic applications.
Journal of Alloys and Compounds, 2015
The structural stability and ground state electronic properties of Fe/AgCl/Fe (0 0 1) junctions w... more The structural stability and ground state electronic properties of Fe/AgCl/Fe (0 0 1) junctions with c(2 Â 2) Fe/AgCl (0 0 1) heterointerfaces are studied by means of ab initio surface Green's function technique for surface and interfaces. The spin-resolved ballistic conductances across Fe/AgCl/Fe (0 0 1) heterojunctions are determined by using Kubo-Landauer approach. Total energy calculations show that sharp Fe/AgCl (0 0 1) interfaces are possible. The interfacial charge transfer is interface sensitive and generates electrostatic interactions that contribute to the stabilization of Fe/AgCl (0 0 1) interfaces. The magnetism of interfacial Fe layers is robust but is responsive to the interfacial structure. The exchange coupling between Fe electrodes across AgCl barriers shows unexpected oscillations with respect to the spacer thickness that may be related in part with the amount of metal induced gap states in AgCl spacers. A powerful D 1 spin filter effect is evidenced across AgCl barriers. Depending on the interface structure, large magnetoresistance ratios, above 3100%, are predicted. Interfacial interdiffusion may affect the magnetoresistive properties. The lower lattice mismatch at c(2 Â 2) Fe/AgCl (0 0 1) interfaces combined with the strong D 1 direct tunnelling across AgCl barriers make Fe/AgCl (0 0 1) interfaces attractive in the context of magnetoelectronics.
Journal of Applied Physics, 2013
Structural, electronic, and magnetic properties of Fe/CaS (001) interfaces and Fe/CaS/Fe (001) he... more Structural, electronic, and magnetic properties of Fe/CaS (001) interfaces and Fe/CaS/Fe (001) heterostructures have been studied by means of a self-consistent Green's function technique for surface and interfaces implemented within the tight-binding linear muffin-tin orbital formalism. Spin dependent transport properties of the Fe/CaS/Fe (001) tunnel junctions with thin and intermediate barriers, in the current-perpendicular-to-plane geometry, have been determined by means of Kubo-Landauer approach implemented within the tight-binding linear muffin-tin orbital formalism. A small charge rearrangement is evidenced at the Fe/CaS (001) interfaces. The iron interfacial magnetic moments are enhanced over the bulk value. A small exchange coupling with the sign depending on the Fe/CaS (001) interface geometric structure and the strength decaying exponentially with the barrier is evidenced. Interfacial charge transfer, interface iron magnetic moments, and tunneling currents are sensitive to the interfacial structure. Interface resonant states have a decisive role in the tunneling process and the main contribution to the current in the ferromagnetic state of the junction is given by the minority-spin electrons. V C 2013 American Institute of Physics.
The pressure dependences of crystal structures and magnetic properties of YCo5 and GdCo5 compound... more The pressure dependences of crystal structures and magnetic properties of YCo5 and GdCo5 compounds are analysed based on band structure calculations. Isomorphic transitions were evidenced for relative volumes v/v0 = 0.91 and 0.86, for YCo5 and GdCo5, respectively. At the transition, there is a higher decrease of cobalt moments at 3g sites as compared to those located in 2c ones. The induced polarizations on Y4d and Gd5d bands, by short range interactions, are linearly dependent on the magnetizations of cobalt atoms situated in their neighborhood. The isomorphic transitions are analysed in correlations with band structures.
Surface Science, 2004
ABSTRACT The electronic structure and magnetic properties of Fe/GaAs/Fe (001) tunnel junction hav... more ABSTRACT The electronic structure and magnetic properties of Fe/GaAs/Fe (001) tunnel junction have been studied using a first-principles Green's function technique, based on the tight-binding linear muffin-tin orbital method in its atomic spheres approximation, in conjunction with the coherent potential approximation to describe the disorder effects such as the interdiffusion at the interface. The results show that at the Fe/GaAs interface there is a charge transfer from iron to the semiconductor region and an enhancement of Fe magnetic moment. The magnetic properties are found to be sensitive to the interface terminations and influenced by the interdiffusion. The spin dependent transport properties are also discussed.
physica status solidi (c), 2006
Journal of Magnetism and Magnetic Materials, 2002
The Y3Co11−xMxB4 compounds with M=Cu or Al, for x⩽3, crystallize in a hexagonal structure having ... more The Y3Co11−xMxB4 compounds with M=Cu or Al, for x⩽3, crystallize in a hexagonal structure having P6/mmm space group. The compounds are ferromagnetically ordered for x⩽3 (M=Cu) and x<2 (M=Al). The cobalt magnetic moments are very sensitive to exchange interactions. The results of band structure calculations were correlated with those obtained from magnetic measurements.
Journal of Applied Physics, 2004
The electronic structure and magnetic properties of semi-infinite Cu (001)/M/Cu/M/semi-infinite C... more The electronic structure and magnetic properties of semi-infinite Cu (001)/M/Cu/M/semi-infinite Cu (001) multilayer systems with M=Fe, Co, or Ni have been studied by means of a first-principle Green's function technique based on the tight-binding linear muffin-tin orbital method. The results show that at the M/Cu (M=Fe or Co) interfaces there is a net charge transfer from iron and cobalt atoms
Journal of Applied Physics, 2011
The magnetic and transport properties of Fe-Pd/Rh(Ir)/Fe-Pd heterostructures have been analyzed b... more The magnetic and transport properties of Fe-Pd/Rh(Ir)/Fe-Pd heterostructures have been analyzed by means of a first principles Green's technique for surfaces and interfaces, implemented within tight-binding linear muffin-tin method. The effects of variable thicknesses both for spacers and magnetic layers on the magnetic and transport properties were analyzed. The spin-dependent transport properties are determined in the ballistic limit by means of linear response of Kubo approach implemented within tight-binding linear muffin-tin orbital formalism. A correlation between the interlayer exchange coupling, conductances, giant magnetoresistances and magnetic properties are shown. The magnetic disorder, simulating the effect of temperature on the interlayer exchange coupling and transport properties, are also discussed.
Journal of Alloys and Compounds, 2014
Neutron diffraction measurements were performed on HoCo 2 in the pressure range p 6 4.8 GPa. The ... more Neutron diffraction measurements were performed on HoCo 2 in the pressure range p 6 4.8 GPa. The evolutions with pressure of holmium and cobalt moments were correlated with those obtained from band structure calculations. Magnetic properties of Ho x Y 1Àx Co 2 compounds with x 6 0.3 were also investigated in a large temperature range. The magnetic behaviour of cobalt in the above system has been analysed in spin fluctuations model.
Journal of Alloys and Compounds, 2013
ABSTRACT The crystal structure and magnetic properties of TbCo2 compound have been analyzed by ne... more ABSTRACT The crystal structure and magnetic properties of TbCo2 compound have been analyzed by neutron diffraction, at pressures up to 4.1 GPa in the temperature range 10–300 K. A rhombohedral type structure of type is shown below Curie temperature. The distortion degree of structure increases with pressure as well as when lowering temperature. The temperature dependences of terbium and cobalt moments can be described by Brillouin functions. The Curie temperatures decrease linearly with pressure with a slope of dTc/dP = −9 K/GPa. The evolution with pressure of the cobalt magnetic moments and Tb5d band polarizations are theoretically analyzed. The experimental data are well described by band structure calculations. The magnetic behavior of cobalt in heavy rare-earth RCo2 compounds is analyzed in spin fluctuations model. A gradual quenching of spin fluctuations by internal field was shown.
Journal of Alloys and Compounds, 2014
Structural, electronic and spin-dependent transport properties of Fe/NaCl/Fe (0 0 1) tunnel junct... more Structural, electronic and spin-dependent transport properties of Fe/NaCl/Fe (0 0 1) tunnel junctions with c(2 Â 2) structure are studied by means of first-principles calculations. Several Fe/NaCl (0 0 1) interfaces are considered and their stability is analyzed. The interfacial charge transfer has an important role in stabilizing Fe/NaCl (0 0 1) interfaces. Interfacial iron magnetic moments are enhanced over the bulk value. Fe induced gap states are observed in barrier layers on both Na and Cl ions. Small exchange couplings with exponential decays as function of the barriers thickness are evidenced. Resonant tunnelling plays a major role on the spin-polarized transport properties. High magnetoresistance ratios comparable to Fe/MgO/Fe junctions are predicted. Total energy calculations show that interfacial interdiffusion is not favourable but the disorder at interfaces may strongly affect the electronic transport properties. Absence of interfacial interdiffusion together with the small lattice mismatch between Fe and NaCl layers are important advantages of Fe/NaCl/Fe (0 0 1) junctions for the purpose of spintronic applications.