Coercivity and its thermal dependence in microsized magnetic particles: Influence of grain boundaries

Abstract

Fe73.5Si13.5B9Nb3Cu1 powder particles have been obtained by gas atomization. Magnetization curves and coercivity were studied for particles ranging in size up to 1000 μm. The overall magnetic behavior of such material is a consequence of compositional heterogeneity of the microstructure as a whole. Anomalous temperature variation of coercivity (Hc) (i.e., a decrease in Hc with decreasing temperature) together with a decrease of saturation magnetization has been observed for less than 25 μm size. The origin of this behavior has been ascribed to metastable FeCu and FeNbSi phases in combination with an Fe-rich one. Making magnetic powders with coercive fields of the order of mOe remains a challenge for researchers. Our experiment has allowed us, at low temperature, achieving a coercive field of 9 Oe, much lower than those observed so far in this type of materials. This behaviour has been related with a FeCu phase present on grain boundaries.

Optimization of Single α-Phase for Promoting Ferromagnetic Properties of 44Fe–28Cr–22Co–3Mo–1Ti–2V Permanent Magnet with Varying Co Concentration for Energy Storage

“…It was noted that the peaks broadening corresponds to angles of 44.5 and 65 with a maximum peak intensity from 3000 to 4500 cps related to the (110) and (200) crystal plane with a bcc structure. The bcc crystal structure corresponds to (100), (110) and (200) crystal planes whose existence proves the single α-phase solid solution material which is in agreement with the literature [ 16 , 17 , 18 ]. The bcc structure at the ridge regime temperature from 620 to 645 °C decomposes into two isomorphic phases α 1 and α 2 with a composition of Fe–Co and Cr–Mo.…”