Exchange-Bias Effect in Bulk Perovskite Manganites

Abstract

In this chapter, mainly the papers devoted to the exchange-bias (EB) effect in bulk perovskite manganites that were published during last 5–6 years are reviewed. The basic magnetic properties of mixed-valence perovskite manganites are discussed. These compounds exhibit very rich phase diagrams, since several phases, differing in magnetic, structural, and electronic properties, may coexist in the same sample. It is stressed that the most relevant feature leading to an appearance of EB is an intrinsic phase separation that occurs in manganites. Most relevant scenario for the EB effect in bulk manganites is the coexistence of ferromagnetic clusters distributed in an antiferromagnetic matrix, as strength of the EB effect strongly depends on the size of ferromagnetic clusters. It is shown that EB may be effectively tuned by chemical substitutions and/or by hydrostatic pressure. The relation between magnetization-reversal phenomenon (consisting in an alignment of spins in the direction opposite to an applied magnetic field) and tunable EB is discussed. The EB effect in double perovskites is discussed, with particular attention to a spontaneous hysteresis loop shift after zero-field cooling (so-called spontaneous EB). Comparison of the EB effect in manganites and in other perovskites (cobaltites, ruthenites, and orthoferrites) is made.