磁场诱导Gd_5Ge_4体系的低温输运跳跃和相分离研究  

STUDY OF TRANSPORT JUMP INDUCED BY MAGNETIC FIELD AT LOW TEMPERATURE AND PHASE SEPARATION IN Gd_5Ge_4 ALLOYS

作　　者：张晓勇[1] 刘永生[1] 曹桂新[1] 敬超[1] 曹世勋[1] 张金仓[1] 

机构地区：[1]上海大学物理系,上海200444

出　　处：《低温物理学报》2006年第4期305-310,共6页Low Temperature Physical Letters

基　　金：国家自然科学基金(项目编号:10574087);上海市科委重点基础研究项目(项目编号:C14039);上海市重点学科(项目编号:T0104)资助的课题.~~

摘　　要：报告了作者对Gd_5Ge_4合金样品进行了磁化和电输运测量的研究结果,实验表明,磁化强度随外磁场的增加而出现台阶式跳跃,磁转变的可逆性与温度存在有密切的关联.在由磁场导致的磁转变附近电阻率随着磁场的增加亦表现出台阶式磁电阻现象,并在不同温区表现出正负不同的磁电阻效应,4.2K时呈现正磁电阻效应,而在16和20K时呈现出负磁阻效应,即铁磁相的阻值小于反铁磁相的阻值.结果证明了在Gd_5Ge_4中存在的典型相分离特征,从而在磁场诱导下发生了反铁磁到铁磁的转变,并对这种奇异磁电阻效应的物理机制进行了讨论.The magnetization and electrical transport induced by magnetic field have been systemically studied for Gd5 Ge4 alloy. The results show that step magnetization occurs with increasing the magnetic field, and reversibility of magnetic transition is dependent on temperature. Concomitant to magnetic transition induced by magnetic field, step mangetoresistance takes place with increasing the magnetic field, and positive or negative mangetoresistance effect is dependent on temperature. At 4.2 K, the magnetoresistance is positive. At 16 and 20 K, the magnetoresistence is negative, indicating magnetoresistance of ferromagnetic phase is higher than that of antiferromagnetic phase. The results proved the existence of phase separation in Gd5 Ge4 compound and magnetic transition induced by magnetic field from antiferromagnetic phase to ferromagnetic phase. Physical mechanism about the strange magnetoresistance effect has been discussed.

关 键 词：Gd5Ge4合金 相分离 台阶式磁化 磁电阻效应 

分 类 号：O482.5[理学—固体物理]