相分离Gd_5Ge_4合金的低温磁化行为及温度依赖性研究

系统研究了Gd_5Ge_4合金的晶体结构和低温磁化行为.结果表明,Gd_5Ge_4具有相分离特征,低温下出现反铁磁(AFM)和铁磁(FM)共存现象.由于相分离的存在导致127K时发生奈尔反铁磁转变.在外磁场诱导下,在4.2K以下发生AFM-FM磁转变,并导致台阶式磁化现象发生,但仅发生在第一次外加磁场增加过程中,表现出磁不可逆性.随磁场升高,在10K以下体系存在类台阶式响应和不可逆的磁滞行为,并在5572kA/m下均达到饱和磁化.在温度50～60K温区,磁循环所出现的台阶式磁化转变则是完全可逆的,更高温区域则表现为部分铁磁直至室温下的顺磁特性.

Magnetization behavior at low temperature and its dependence on temperature in phase separated Gd_5Ge_4 alloy

Crystal structure and magnetization behavior at low temperature were studied systematically for Gd_5Ge_4 alloy. The results show that Gd_5Ge_4 is a phase-separated alloy and has antiferromagnetic (AFM) state and ferromagnetic (FM) state coexisting at low temperature. Abnormal Neel transition occurs at 127K due to phase separation. Below 4. 2K,AFM-FM transition induced by magnetic field can occur in Gd_5Ge_4, the transition is the main reason for magnetization step transition, and the magnetic transition only occurs when the magnetic field firstly increases, so it is irreversible. With magnetic field increasing,below 10K, there exist magnetization step behavior and hysteresis behavior, and the magnetization value reach saturation at 5572kA/m. At temperature 50-60K, the second magnetization almost goes along the first magnetization path, so the magnetization is entirely reversible. The Gd_5Ge_4 alloy is partly ferromagnetism below 120K and is completely para-magnetism at room temperature.