Ni_(52)Mn_(24)Ga_(24)金属间化合物的单晶生长和磁性功能

SINGLE CRYSTAL GROWTH AND MAGNETIC FUNCTION OF Ni_(52)Mn_(24)Ga_(24) INTERMETALLIC COMPOUND

研究了 Ｎｉ５２Ｍｎ２４Ｇａ２４合金单晶在磁场作用下能产生的目前最大的磁致伸缩应变．发现了该材料的双向相变应变效应以及磁场对此的增强现象．在 １．２ Ｔ磁场的作用下，可逆的相变应变达 ４％以上实现这一结果的关键条件是马氏体变体的择优取向报道了获得马氏体变体的择优取向样品的单晶生长特性和后处理方法根据前人报道的理论模型分析了实验结果，指出磁感生应变的物理机制是磁场提供的

The Ni52Mn24Ga24 single crystals showed a large stain of 1% with a temperature hysteresis of only 10 K unneeded the association of external stress. The magnetic-field-enhanced strain up to 4% can be obtained by applied a field of 1.2 T in the [001] direction of the sample. The magnetostriction is up to 1% at the temperature close to the martensitic transition, which is much larger than that of (Tb, Dy)Fe2. These results are related to the preferential orientation of the martensitic variants in the single crystalline samples. The metallurgical observation showed that the disordering infernal stress in the sample can be eliminated by a two-step annealing, which avoids the random orientation of the variants. The directional internal stress caused by the directional solidification in turn makes a large fraction of variants preferentially oriented. In such samples, the applied magnetic field of 1.2 T is more effective to rearrange the variants than the residual internal stress during the martensitic transition. The sign of the strain can be changed by changing the field direction, which shows a potential application for fabricating a multi-poles actuator device. Based on the previous modeling, the mechanism of the magnetic field induced strain has been discussed.