Study on Electrical and Magnetic Properties of Nd–Co Co-Substituted M-type Strontium Ferrite Suitable for Microwave Devices

Solid-state method was used to make Nd–Co co-substituted strontium ferrite (NdxSr1 − xCoxFe12 − xO19, x = 0.00–1.00) samples. When x ≤ 0.20, the coercivity rose from 3353.00 to 4045.20 Oe. The saturation magnetization declined by 2.58 percent, from 64.39 to 62.73 emu/g. At the same time, when x < 0.20, the sample’s resistivity exhibits a unique bimetal-semiconductor transition behavior and the image of resistivity shifts to the low-temperature direction. When x = 0.30, a clear α-Fe2O3 phase appears on XRD pictures. Furthermore, when x ≥ 0.30, the amount of α-Fe2O3 grows as the replacement amount increases. Finally, when x = 1, the sample’s coercivity drops to 600.44 Oe and the saturation magnetization drops to 15.56 emu/g. The magnetic properties of the samples show high coercivity, high saturation magnetization, and their electrical properties show special metal–semiconductor transition behavior.