The phase diagram of the system Mn2−xFexAs0.5P0.5 under pressure is investigated experimentally and theoretically. It is found that the spontaneous and magnetic-field-induced low-temperature phase in the region 0.5⩽x<0.8 does not suffer significant changes under hydrostatic pressure up to 2kbar. Based on ab initio calculations of the electronic structure of the alloys Mn1.5Fe0.5As0.5P0.5, it is established that the degree of filling of the 3d electron band changes upon ferromagnetic polarization and compression of the crystal lattice. A model is proposed by which one can take into account the main features of the antiferromagnetic and canted ferromagnetic structures. The parameters of the model are the degree of filling of the d band, the nonmagnetic electronic density of states, and the intra-atomic exchange integral. Their values are estimated directly from the data of the first-principles electronic structure calculations. It is shown in the framework of the model that the stability of the magnetic characteristics of the canted ferromagnetic structure with respect to pressure is due to an increase of the number of electrons in the magnetically active band upon a decrease of the unit cell volume.
В рамках модели взаимодействующих параметров магнитного и структурного порядков проведен анализ магнитокалорических свойств систем, обладающих разнесенными (совмещенными) по температуре магнитными (парамагнетизм (PM)−ферромагнетизм (FM)) и структурными (гексагональная−орторомбическая решетки) переходами. Показано, что в зависимости от характера сочетания низкосимметричной орторомбической (Pnma) и высокосимметричной гексагональной (P6 3/mmc) фаз с ферромагнитным порядком можно ожидать усиления или ослабления магнитокалорических характеристик системы при совмещении структурного (P6 3 /mmc−Pnma) и магнитного (PM−FM) переходов.
The effect of high pressure and magnetic field on the stability of magnetic phase transitions in (Fe 1Àx Ni x ) 49 Rh 51 has been studied. It has been shown that the increase in the Ni content suppresses the stability of the low-temperature antiferromagnetic phase and leads to its disappearance. Pressure on the other hand restores the stability to the antiferromagnetic order. These findings are explained using first-principles band-structure calculations.
The temperature dependence of magnetic susceptibility in ferrous fluorsilicate under all-sided compression is studied. It is proved that under pressure the anisotropy increases in the basal plane and loss of orientation by water octahedra is observed. This may be interpreted as the appearance of an esay-axis. The energy spectrum of the two-valent Fe ion is estimated for different pressures. M3yYelIa TeMnepaTypHaR 3aBHCBMOCTb MarHBTHOn BOCnPHHM9P3BOCTH @TOpCBJIBKaTa XieJIe3a B YCJIOBBRX BCeCTOpOHHerO CWaTBH. DOICa3aH0, YTO nOz DefiCTBBeM RBBJIeHIIfl paCTeT aHIX30TpO~BR B 6 a 3~c~o i i IIJIOCICOCTA II Ha6~1WnaeTcH pa30pBeHTaqBR OKTa3apOB CneKTp BOHa ~ByXBaJIeHTHOrO XieJIe3a DJIR pa3JIP39HbIX AaBJIeHIIfi. BOAM. TO MOXHO TpaHTosaTb HaK nomneme nerHo8 om. PaccmTaH a~epre~tlsec~rnfi
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