Grain modification approaches in mixed-valence manganites toward enhanced LFMR

Abstract

Mixed-valence manganites have attracted considerable attention due to their remarkable colossal magnetoresistance (CMR) effect, which makes them promising candidates for magnetic sensing and spintronic applications. However, the CMR effect is typically significant only at high magnetic fields near the Curie temperature, limiting its practical utility. As a result, enhancing low-field magnetoresistance (LFMR) has become a critical focus in manganite research. Grain modification has emerged as a practical approach for LFMR enhancement, primarily by promoting spin-polarised tunnelling across grain boundaries. This review presents recent progress in grain modification for enhanced LFMR in mixed-valence manganites, covering grain size reduction in manganite compounds and the incorporation of secondary phases into manganite composites. We analyse how these methods influence magnetotransport properties, particularly emphasising the interplay between the double exchange (DE) mechanism and Jahn-Teller (J-T) distortion. Despite promising results, challenges remain in controlling grain boundary characteristics and achieving significant LFMR at room temperature. The review also identifies key research gaps and proposes future directions. This work aims to consolidate current understanding and stimulate further advancements in designing high-performance manganite-based materials for spintronic applications.