Some applications of NMR to the study of magnetically-ordered materials with emphasis on the short-range order in (Fe-B)-based crystalline and amorphous alloys

Abstract

In this review, we summatize recent developments in nuclear magnetic resonance (NMR) studies on (Fe-B)-based crystalline and amorphous alloys, focusing on the application of NMR in identifying the existence of short-range order (SRO), determining the types of SRO, characterizing the behavior of the SRO and exploring the effect of the SRO on the magnetic properties for the Fe-B system. NMR experiments reveal that certain local environments surrounding the B atoms exist in both crystalline and amorphous Fe-B alloys. The type of SRO existing in this rapidly quenched system can be either o-Fe 3B or bct-Fe 3B, or a mixture, depending on the composition and processing factors, especially the carbon content and quenching speed. The SRO originates from a strong covalent bonding between the B and Fe atoms. As this interaction plays the same role in both crystalline and amorphous Fe-B alloys, the SRO which occurs in the amorphous Fe-B alloys is similar to the SRO which exists in their crystalline counterparts. NMR, in combination with magnetization measurements, provides evidence indicating that the SRO existing in the amorphous Fe-B alloys has a significant effect on their soft magnetic properties and that different types of SRO may act differently, thus providing an opportunity to improve the magnetic properties by changing the SRO. In connection with reviewing the achievements of NMR studies in recent years, brief comments concerning the advantages and potential of NMR experiments in the investigation of other magnetically-ordered materials will also be presented.