ฉันต้องใช้ภาษาอังกฤษถูกหลักไวยากรณ์
Some special nickel iron alloys have very high magnetic susceptibility and very low remanent magnetization. Common examples are Permalloy(78.5% Ni 21.5% Fe) and Mumetal (77% Ni, 16% Fe, 5% cu, 2% Cr The preparation of these alloys involves annealing at very high temperature(1100-1200 C) to remove lattice defects around which internal stress could produce magnetostric- tive energy. After this treatment the coercivity of the alloy is very low(i.e., its magnetization can be changed by a very weak field) and its susceptibility is so high that the Earth's field can induce a magnetization in it that is a considerable proportion of the saturation value.