Magnetic entropy change and magnetoresistance in the LaFe11.375Al1.625 compound (original) (raw)
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Journal of Physics: Condensed Matter, 2003
A large change in the magnetic entropy, | S|, was observed in the Febased NaZn 13-type compound LaFe 11.375 Al 1.625 , which was nearly temperature independent over a wide temperature range (an about 70 K span from ∼140 to 210 K). This behaviour of the magnetic entropy change is associated with two closely spaced magnetic transitions. X-ray diffraction investigation at different temperatures indicates that the crystal structure remains cubic, of NaZn 13 type, when the magnetic state changes with temperature, but the cell parameter changes dramatically at the first-order transition point.
Magnetic entropy change in LaFeSi intermetallic compounds
2002
compounds with 2.6, and 2.8 have been carefully prepared and characterized. X-ray powder diffraction patterns confirm that the samples crystallize in a single-type phase. Magnetic measurements were carried out in a SQUID magnetometer. The Curie temperature of samples decreases nearly 50 K with increasing from 2.4 to 2.8. Around the samples exhibit a typical second-order phase transition; and no trace of first-order itinerant electron metamagnetic transition is found.
Chinese Physics, 2004
Effect of Co substitution on magnetic properties and magnetic entropy changes in LaFe11.83Si0.94Al0.23 compounds has been investigated by means of magnetization measurements. X-ray diffraction shows the prepared compounds to be single phase with the cubic NaZn13-type structure. Substitution of Co for Fe leads to an increase of Curie temperature of the material. The magnetic entropy changes in LaFe11.83Si0.94Al0.23 and LaFe11.03Co0.80Si0.94Al0.23
Effects of heat treatment on crystal structure and magnetic properties of LaFe12−xAlxMn compounds
physica status solidi (b), 1996
Thc LaFel~-.Al,.Mn (r: = 2, 3, 4, 5, 6, 7) alloys have been annealed at different temperatures and for different periods. The crystal structures and magnetic properties of these compounds are investigated by X-ray diffraction and ac susceptibility measurements. The results indicate that the NaZnl3-type structure is slightly sensitive to Mn-doping. However, the rnagnctic properties of thesc compounds are strongly related to the annealing temperature and period. A structural transition occurs in LaFesA17Mn after annealing at 773 K for about three months. A magnetic transition from ferromagnetic to paramagnetic state is found in LaFe7AlsMn after annealing at, 773 K for two months.
Journal of Magnetism and Magnetic Materials, 2004
Magnetic and magnetocaloric properties of the series La 0.7 Sr 0.3 Mn 1Àx Ni x O 3 (x ¼ 0:00; 0.01, 0.02, 0.03, and 0.05) have been investigated. The X-ray diffraction analysis shows that all perovskites studied have the rhombohedral structure. The field-cooled and zero-field-cooled thermomagnetic curves measured at low field show that there is spinglass (or cluster-glass)-like state in the samples. It is found that the magnetic-entropy change jDS max j has reached the highest value of 3.54 J/kg K at 13.
J. Appl. Phys, 2000
VPS Awana,a) E. Schmitt, and E. Gmelin Max-Planck-Institut für Festkörperforschung Heisenbergstr-1, D-70569 Stuttgart, Germany Anurag Gupta, A. Sedky, and AV Narlikar National Physical Laboratory, KS Krishnan Marg, New Delhi 110012, India OF de Lima and ...
Physical Review B, 1985
Cubic La(Fe"A1~)» intermetallic compounds can be stabilized with iron concentration x between 0.46 and 0.92 in the NaZn»-type structure (D23) with Fm3c (O~) space-group symmetry. Here the Fe-Fe coordination number can increase up to 12. At low x values, a mictomagnetic regime occurs with distinct cusps in the ac susceptibility. With the increase of the iron concentration, a soft ferromagnetic phase is found which at lower temperatures shows anisotropy effects related to reentrant mictomagnetic behavior. Finally, for x &0.86, antiferromagnetic order appears along with a sharp metamagnetic transition in external fields of a few teslas. The saturation magnetic moment increases linearly with x from 1.4p~/Fe to 2.1p~/Fe throughout the ferromagnetic and antiferromagnetic regime. The breakdown of long-range ferromagnetic order at high x values can be explained by modifications of the iron moment and their coupling at a large Fe-Fe coordination number. However, with application of a magnetic field, the ferromagnetic state can be fully recovered. The room-temperature resistivity decreases with increasing x from 200 to 160 pQ cm. The low-temperature slope dp/dT is related to the magnetic order, being negative in the antiferromagnetic state and positive in the ferromagnetic state. The metamagnetic transition causes a decrease of the resistivity of about 20% and a sign change in dp/dT. This behavior is discussed in terms of the two-current model. The thermal expansion exhibits a strong Invar character and is described by a combined band and local-moment model which allows calculations of corresponding magnetovolume coupling constants. The metamagnetic transition causes a large magnetic striction.
Critical behavior and magnetic entropy change in La0.7Ca0.3Mn0.9Zn0.1O3 perovskite manganite
Current Applied Physics, 2011
We studied the critical behavior and magnetic entropy change in a perovskite-manganite compound of La 0.7 Ca 0.3 Mn 0.9 Zn 0.1 O 3 around its Curie temperature of T C ¼ 206.75 K. Experimental results revealed that the sample exhibited the second-order magnetic phase transition with the exponents b ¼ 0.474 and g ¼ 1.152 close to those expected from the mean-field theory (b ¼ 0.5 and g ¼ 1.0). In the vicinity of T C , the magnetic entropy change DS M reached maximum values of 1.1, 1.7, and 2.7 J/kg K under magneticfield variations of 10, 20, and 35 kOe, respectively. These DS M values are much lower than those reported previously on the parent compound of La 0.7 Ca 0.3 MnO 3 . The nature of this phenomenon is discussed by means of the characteristics of the magnetic phase transition, and critical exponents.