The Co-doped Tb 0.36Dy 0.64Fe 2 magnetostrictive alloys with a wide operating temperature range

Abstract

Magnetostrictive alloys with a wide operating temperature range from −80 to 150 °C were developed by changing the Tb/Dy ratio of Tb x Dy 1− x Fe 2 from 0.3/0.7 to 0.36/0.64 and Co partly substituting for Fe. The structure, Curie temperature, AC susceptibility, magnetization, magnetocrystalline anisotropy constant K 1 and magnetostriction of Tb 0.36Dy 0.64(Fe 1− y Co y ) 2 ( y = 0.0 , 0.1, 0.2) alloys were investigated. It was found that the matrix of Tb 0.36Dy 0.64(Fe 1− y Co y ) 2 alloys keeps the MgCu 2-type cubic Laves structure with a small amount of R-rich phase. A small amount of R 2(Fe,Co) phase was also detected when y = 0.2 . The Curie temperature T c of Tb 0.36Dy 0.64(Fe 1− y Co y ) 2 alloys is higher than Tb 0.3Dy 0.7Fe 2 and increases drastically with increasing Co content from 387.1 °C for Tb 0.36Dy 0.64Fe 2 to 416.7 °C for Tb 0.36Dy 0.64(Fe 0.9Co 0.1) 2 and 433.3 °C for Tb 0.36Dy 0.64(Fe 0.8Co 0.2) 2. The spin reorientation temperature T r decreases from −12 °C for Tb 0.3Dy 0.7Fe 2 to −94 °C for Tb 0.36Dy 0.64Fe 2. It increases slightly with increasing Co content. The magnetocrystalline anisotropy coefficient K 1 of Tb 0.36Dy 0.64(Fe 1− y Co y ) 2 alloys is greater than Tb 0.3Dy 0.7Fe 2 but decreases with increasing Co content. The saturation magnetization M s of Co-doped alloys is lower than that of Tb 0.3Dy 0.7Fe 2 and decreases with increasing Co content. The magnetostriction of Tb 0.3Dy 0.7Fe 2 and Tb 0.36Dy 0.64(Fe 1− y Co y ) 2 alloys was examined against applied magnetic field up to 5 kOe in the temperature range from −80 to 150 °C.The temperature coefficient of magnetostriction ( Δ λ / Δ T ) of Tb 0.3Dy 0.7Fe 2 and Tb 0.36Dy 0.64(Fe 1− y Co y ) 2 alloys was also calculated by linearly simulating the magnetostriction-temperature curve, showing that the absolute value of Δ λ / Δ T at 5 kOe magnetic field is 1.17 ppm/°C for y = 0.1 and 1.35 ppm/°C for y = 0.2 , smaller than that of Co free samples, which is 2.43 ppm/°C for Tb 0.36Dy 0.64Fe 2.