The approach to saturation magnetization of nanocrystalline Fe90Zr7B3 alloy

The approach to the saturation magnetization of a nanocrystalline Fe90Zr7B3 alloy has been studied by means of differential magnetic susceptometry. Th e influence of the microstructure of the alloy on the approach to saturatio n magnetization has been studied. It has been found that for the optimum he at-treated sample (heated at 923 K for 0.25 h), which had an average grain size of 12 nm and a coercivity, H-c = 6.4 A m(-1), the approach to saturati on magnetization can be expressed using the law of approach to saturation m agnetization, chi = aM(s)H(-2) + 2bM(s)H(-3) + c/2(H-1/2) (where chi is the differential magnetic susceptibility, M, is the saturation magnetization, H is the magnetic field, and a, b and e are constants), without the H-3 ter m, while for the sample heated at 923 K for 240 h, which had an average gra in size of 82 nm and a coercivity, H-c = 950 A m(-1), the approach to satur ation magnetization cannot be expressed in the same form. For both samples, the magnetic-anisotropy-related H-3 term cannot be found. As a result, the magnetic anisotropy in this nanocrystalline alloy cannot be determined by using the law of approach to saturation magnetization. The measurement with the differential susceptometer has been compared with the measurement made on the SQUID magnetometer. The result has shown that the measurement of di fferential susceptibility using a long, ribbon sample on the differential s usceptometer is more reliable than that using a small sample on the SQUID.