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Pressure effect on magnetic phase transitions in La 0.75 Sm 0.25 Mn 2 Si 2

2005; American Physical Society; Volume: 72; Issue: 6 Linguagem: Inglês

10.1103/physrevb.72.064446

1550-235X

Е. Г. Герасимов, Н.В. Мушников, T. Goto,

Iron-based superconductors research

The magnetization of a quasisingle-crystalline ${\mathrm{La}}_{0.75}{\mathrm{Sm}}_{0.25}{\mathrm{Mn}}_{2}{\mathrm{Si}}_{2}$ sample was measured under high pressures to $P=1.2\phantom{\rule{0.3em}{0ex}}\mathrm{GPa}$. The compound exhibits four different spontaneous magnetic phase transitions: the ordering of Sm sublattice at a critical temperature ${T}_{\mathrm{Sm}}=14\phantom{\rule{0.3em}{0ex}}\mathrm{K}$, the ferro-antiferromagnetic phase transition at ${T}_{\mathrm{AF}}=150\phantom{\rule{0.3em}{0ex}}\mathrm{K}$, the Curie temperature of the ferromagnetic phase at ${T}_{\mathrm{C}}=305\phantom{\rule{0.3em}{0ex}}\mathrm{K}$, and finally, the transition to the paramagnetic state at ${T}_{\mathrm{P}}=403\phantom{\rule{0.3em}{0ex}}\mathrm{K}$. The changes of the critical temperatures of the spontaneous magnetic phase transitions under pressure are $\ensuremath{-}0.6$, $+203$, $\ensuremath{-}12$, and $\ensuremath{\sim}\ensuremath{-}60\phantom{\rule{0.3em}{0ex}}\mathrm{K}∕\mathrm{GPa}$, respectively. The temperature range of ferromagnetic phase shrinks with increasing pressure, and at $P\ensuremath{\geqslant}0.6\phantom{\rule{0.3em}{0ex}}\mathrm{GPa}$ no ferromagnetic ordering of Mn magnetic moments is observed. For the antiferromagnetic phase, application of a relatively low magnetic field produces a sharp first-order field-induced metamagnetic transition. The critical field of the metamagnetic transition depends on the direction of applied field and increases with increasing pressure. The nature of various magnetic phase transitions in $R{\mathrm{Mn}}_{2}{X}_{2}$ compounds is discussed using a thermodynamic analysis of the obtained results and a phenomenological model of the step change of $\mathrm{Mn}\ensuremath{-}\mathrm{Mn}$ interlayer exchange interaction at the transition.