Magnetic properties of Pr 2 (Fe 1-x Co x) 14 B compounds (original) (raw)
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Magnetic properties and magnetocaloric effect in compound PrFe 12 B 6
Chinese Physics B, 2010
Structural properties, magnetization and magnetocaloric effect measurements in the compounds based on lanthanum-strontium-bismuth manganites La 0.7 Sr 0.3Àx Bi x MnO 3 (LSBiMO) with 0.05 6 x 6 0.30 have been performed. The valence states of elements entering into the composition of investigated LSBiMO samples were analyzed for x = 0.15 and 0.3 using the HR XPS spectra of Bi 4f, La 3d, Mn 3s and Sr 3d. According to X-ray powder diffraction data the crystalline structure of the samples is perovskite-like with a small rhombohedral distortion. The a and c lattice parameters and unit cell volume V are established to increase with increasing Bi content. All the manganites show ferromagnetic-like ordering with second order phase transition to paramagnetic state. The Curie temperature and magnetization decrease at substitution of Sr 2+ for Bi 3+ ions. The magnetic entropy changes were calculated using the field dependence of isothermal magnetization in the terms of the thermodynamic Maxwell relation. The maximum magnetic entropy change value was shown to be 0.94 J kg À1 K À1 for x = 0.05 for a field change of 1 T.
Journal of Applied Physics, 1999
The 295 K unit cell parameters of Pr 2 Fe 17 H x , where x is 0, 1, 2, and 3, have been determined by x-ray diffraction. Upon hydrogenation, the unit cell volume expands anisotropically with a 1.2% expansion of the a axis and no expansion of the c axis for xϭ3. The Curie temperatures are 286, 374, 440, and 484 K, for xϭ0, 1, 2, and 3, respectively. The Mössbauer spectra have been measured between 4.2 and 295 K, and the spectra of Pr 2 Fe 17 H and Pr 2 Fe 17 H 2 , obtained above 80 K, and those of Pr 2 Fe 17 H 3 , obtained above 120 K, have been analyzed with a seven sextet model, a model which corresponds to basal magnetic anisotropy. The Mössbauer spectra of Pr 2 Fe 17 H 3 change dramatically upon cooling below 80 K, and between 4.2 and 75 K they are well fit with a four sextet model which corresponds to axial magnetization. Between 80 and 120 K, the spectra are very complex and, hence, the Mössbauer spectra reveal a spin reorientation which occurs between 80 and 120 K in Pr 2 Fe 17 H 3 .
Magnetic properties of Pr[Fe(CN)6] · 5H2O
physica status solidi (a), 2003
ABSTRACT Magnetic properties of Prussian blue analogues, the molecule-based ferrimagnet Pr[Fe(CN)6] · 5H2O, are presented. The zero-field-cooled magnetisation curves deviate from the field-cooled magnetisation measurements M(T) below certain temperature Tf = 14.5 K, and show a broad maximum at about T = 12 K. Such a behaviour of M(T) is typical for the small particles system or for non-interacting magnetic clusters. The saturation magnetic moment μs = 2.02 μB, determined from M(1/H) curves, agrees very well with the theoretical value. The Curie temperature Tc = 14.8 K were determined from M2(T) curves. The M(H) curve shows hysteresis behaviour at T = 4.5 K. Magnetic susceptibility χ obeys Curie–Weiss law very well above Tθ = 30 K with μeff = 3.8 μB and = –18.6 K. The changes in shapes of low-temperature 1H-solid-echo spectra reflect the changes in the magnetic state of the sample.
Magnetoresistance and electrical resistivity studies in Pr2(Co1−xFex)17
Physica B+C, 1985
A thorough investigation of Pr2(Co,_ xFex),7 pseudocompounds has been done with high accuracy electron transport measurements (p, dp/dT), dp(T, Z7) in the ranges 77 < T 6 800 K, 0 s H L 10 kOe. The Curie points (T,) and the spin reorientation transition temperatures (TJ were accurately located, and the corresponding critical behaviour properly displayed. The role of several different magnetlzatlon processes was analyzed. in connection with the changes of the anisotropy constants with composition or temperature. New evidence is presented for the existence of important flucruations in the Pr3+ spins at temperatures well below the Curie point.
Effect of Al on the magnetic properties of Pr3(Fe1−xAlx)27.5Ti1.5 (x=0.1, 0.2, and 0.3)
Journal of Applied Physics, 2006
The effect of Al on the structural and magnetic properties of Pr3(Fe1−xAlx)27.5Ti1.5 (x=0.1, 0.2, and 0.3) compounds has been investigated by x-ray-diffraction, magnetization, and Curie temperature measurements. All these compounds have formed in monoclinic symmetry with A2∕m space group with Pr(Fe,Ti)12 as secondary phase and traces of α-Fe. The monotonic decreases in MS both at 300 and 80K are discussed on the basis of electron transfer from the 3p band of Al to the 3d band of Fe near EF. The variations in TC are explained using the Friedel approach. In all the compounds, the easy magnetization direction is away from the b axis.
Journal of Alloys and Compounds, 2016
Nanocrystalline Pr 2 Co 7−x Fe x (x 3.5) powder was synthesized by high energy milling and was subsequently annealed at 973 K for 30 min. Their crystalline structures were investigated by means of X-ray diffraction (XRD), X-ray absorption spectroscopy (XAS) and transmission electron microscopy (TEM). Magnetic properties were also studied at room temperature and 10 K as a function of the iron composition. This compounds structure depends on the iron content; for x 1 they crystallize in the Ce 2 Ni 7-type hexagonal structure (space group: P 6 3 /mmc). For 1 < x 3, we observe a mixture of three phases, Pr 2 (Co,Fe) 7 , Pr(Co,Fe) 3 and Pr 2 (Co,Fe) 17 while for larger values of x the Pr 2 (Co,Fe) 7 phase disappears completely. Since the substitution of cobalt by iron in a pure Pr 2 Co 7−x Fe x phase is limited to x 1, a site preference can be suggested. Unfortunately standard XRD cannot be used unambiguously because Co and Fe have too close normal X-ray atomic scattering factors. Among the local and Fe selective available experimental methods, we have chosen to explore the P 6 3 /mmc space group Wyckoff positions for iron by EXAFS at the Fe edge. This study shows that the local iron radial distribution function is much larger than expected for all the specific sites, at least two Fe-Pr distances, except for 12k which gives the best fit. A preferential substitution of cobalt by iron in 12k site is coherent with (i) the EXAFS result (ii) the substitution rate x < 1 (iii) the anisotropic increase of the crystal cell parameters. A mixture of 12k, 6h and 2a cannot be excluded. However, if we assume a unique preferential site, 12k is the only solution. For x 1, the magnetocryslalline anisotropy is observed in Pr 2 Co 7−x Fe x alloys with fairly strong anisotropy fields at room temperature in range from 123 to 136 kOe for x = 0 and x = 1, respectively. For x > 1, the magnetocrystalline anisotropy field of the 2:17 phase is lower than that of the 2:7 phase, which causes a further reduction in anisotropy and coercivity.
Structural and intrinsic magnetic material parameters of Pr3(Fe,Ti)29 and Pr3(Fe,Ti)29Nx
Journal of Magnetism and Magnetic Materials, 1996
We report the study of the structural and the intrinsic magnetic properties of the Pr member of the newly discovered class of R3 (Fe, Ti) 29 compounds and its nitride. The X-ray powder diffraction pattern of the alloy is indexed in monoclinic symmetry with lattice parameters a= 10.647 (1) A ̊, b= 8.6014 (7) A ̊, c= 9.755 (1) A ̊ and β= 96.92 (1)° and the structure is described in the A2/m space group. Atomic positions and bond lengths are given. Nitrogenation results in a lattice expansion of 6.6% corresponding to∼ 4N atoms per ...
Magnetoelastic properties of Pr2Co17−xFex compounds
Journal of Magnetism and Magnetic Materials, 2004
We present a preliminary study of the magnetoelastic properties in some compounds of the Pr 2 Co 17Àx Fe x series (x ¼ 5:1; 11:05). Volume magnetostriction and linear thermal expansion of Pr 2 Co 11.9 Fe 5.1 show a large anomaly at the spin reorientation temperature (T SR E80 K). This anomaly is not present at the spin reorientation transitions in Pr 2 Co 5.95 Fe 11.05. In contrast, the anisotropic magnetostriction shows a similar behaviour in both compounds. The results are discussed in terms of different contributions of the 3d and 4f sublattices to the magnetoelastic properties.
A magnetic and Mössbauer spectral study of PrFe11Ti and PrFe11TiH
Journal of Alloys and Compounds, 2004
The lattice parameters, magnetic and Mössbauer spectral properties of PrFe 11 Ti and PrFe 11 TiH have been measured between 4.2 and 295 K. Both compounds crystallize in the ThMn 12 -type structure. The insertion of hydrogen in PrFe 11 Ti anisotropically expands the unit-cell volume by 0.4%. Both compounds are ferromagnetically ordered with Curie temperatures of 547 and 604 K, respectively. Between 4.2 and 295 K, the easy magnetization direction is within the basal plane along the [1 0 0] direction as indicated by the Mössbauer spectra which have been fit with a model taking into account both the binomial distribution of titanium near neighbors of the iron atoms and the basal orientation of the magnetic moments. (F. Grandjean).