Variations in temperature coefficient of anisotropy and coercivity in finite particles of Nd2Fe14B type recording materials through substitutions

A theoretical and experimental study is reported on how to modify the temperature dependence of coercivity, H_c(T), in R₂F₁₄B type compounds (R=rare earth) through modifications of the temperature dependence of anisotropy field, H_A(T). This is accomplished by partial substitutions on R sites. Experimentally it is found that for Y₂Fe₁₄B fine particles ( approximately 1- mu m), values of H_c are in the range of 1 kOe. For these materials, a slightly positive H_c(T) is obtained near 300 K. Stable H_A(T) and H_C(T) near 300 K are obtained, e.g., with Nd_0.2Y_0.8Fe₁₄B, while strongly increasing H_A(T) and H_c(T) are obtained with small substitutions of Er for Y in Y₂Fe₁₄B. More complex H_A(T) and H_c(T) can be obtained in more complex systems.