诱导的反铁磁→铁磁一级磁相变
(中南大学 应用物理与热能工程系，长沙 410083)
摘 要: 在脉冲强磁场中测量了Gd1-xLaxMn2Ge2(x=0.06，0.07)化合物在不同温度下的磁化曲线。结果表明，当这些化合物处于反铁磁状态的温度范围内时，Mn次晶格中发生了场诱导的从反铁磁状态到铁磁状态的一级磁相变。随着温度的降低，相变临界磁场逐渐增大，达到最大值后，随着温度的进一步降低，临界磁场很快减小；随La含量的增加，相变临界磁场也很快减小。在交换相互作用的分子场模型基础上， 考虑层面间Mn-Mn交换作用随晶格常数a以及温度的变化，从理论上计算了这种场诱导的反铁磁→铁磁一级磁相变所对应的临界磁场，理论计算结果较好 地 描述了临界磁场随温度的变化规律。理论模型也较好地解释了在这些化合物中发生的从亚铁磁结构到反铁磁结构再到铁磁结构的一级自发磁相变。
关键字: 稀土金属间化合物；交换相互作用；磁相变
antiferromagnetism→ferromagnetism
transitions in Gd1-xLaxMn2Ge2
(x=0.06，0.07) intermet
（Department of Applied Physics and Heat Energy Engineering，
Central South University，Changsha 410083，China）
Abstract:The magnetization curves of Gd1-xLaxMn2Ge2(x=006, 0.07)intermetallic compounds were measured in the pulse magnetic field at different temperatures. The results show that the field-induced antiferromagnetism→ferromagnetism transitions in Mn-sublattice are founded in the antiferromagnetic state temperature range. The critical transition field tends to increase with decreasing the temperature，after reaching the maximum，the critical field decreases significantly. With the in crease of the content of La，the critical transition fields also decrease significantly. In the approximation of molecular field of exchange interaction， the critical transition fields are calculated by taking into account of lattice parameter a and temperature dependence of the interlayer Mn-Mn exchange parameter. The theoretical results well describe the temperature dependence of critical transition field. Theory also well explain the spontaneous first order ferrimagnetism→antiferromagnetism→ferrom agnetism transition in the studied compounds.
Key words: rare earth intermetallic compound; exchange in teraction; magnetic phase transition
