(Nd_(0.7)Pr_(0.3))_(60-x)Fe_(30)Al_(10)Cu_x(x=0,1,2,4)大块非晶合金磁性及矫顽力机理

Magnetic Properties and Coercivity Mechanism in the (Nd_(0.7)Pr_(0.3))_(60-x)Fe_(30)Al_(10)Cu_x(x=0,1,2,4) Bulk Amorphous Alloys

采用铜模吸铸法制备了（Nd0.7Pr0.3）60-x Fe30Al10Cux（x=0,1,2,4）大块非晶合金,利用振动样品磁强计（VSM）研究了该合金的磁性能和磁粘滞行为。结果表明,这几种合金都呈现出较好的硬磁性。随着Cu元素的添加,矫顽力略有增加,但是合金的剩磁却没有变化。利用扫描速率法研究了（Nd0.7Pr0.3）60-x Fe30Al10Cux（x=0,1,2,4）大块非晶合金的磁粘滞行为,得到了这几种合金的相关磁性参数：热扰动场Hf为12.1~15.2 m T,热激活体积va为1.5×10^-18~1.9×10^-18 cm^3。在所研究的合金中都存在明显的铁磁交换耦合作用,同时矫顽力与温度之间的关系符合Gaunt提出的畴壁钉扎模型,合金的硬磁性可能是这两方面共同作用的结果。

Bulk amorphous（Nd0.7Pr0.3）60-x Fe30Al10Cux（x=0, 1, 2, 4） alloys with diameter of 2 mm were prepared by argon arc melting and suction casting the molten alloy into a copper mould. The magnetic properties and coercivity mechanism of the alloys were investigated by the measurement of major hysteresis loop, exchange coupling curve（M-H plot）, magnetic viscosity and the temperature dependence of the coercivity. At room temperature, all the alloys exhibit hard magnetic properties. The coercivity increases slightly with increasing the Cu content, while the remanence has the same values. The fluctuation field, Hf, is determined from sweep rate measurement. It is in the range of 12.1~15.2 m T. The thermal activation volume, va, is from 1.5×10^-18 to 1.9×10^-18cm^3. The exchange coupling interaction in all four alloys is confirmed by the M-H plot. The temperature dependence of the coercivity can be well explained by Gaunt＇s strong pinning model of domain walls. The hard magnetic behavior of bulk amorphous（Nd0.7Pr0.3）60-x Fe30Al10Cux（x=0, 1, 2, 4） alloys may be determined by the exchange coupling interaction among clusters and strong domain wall pinning.