Exchange-bias effect in manganite nanostructures

Papers devoted to exchange-bias (EB) effect in manganite nanostructures published recently, that is, within last 5-6 years, are reviewed. It is shown that when the size of magnetic structures is reduced to the nanometer scale, many of their basic magnetic properties, for example, spontaneous magnetization, the magnetic transition temperature, and coercivity, differ significantly from the bulk values and become strongly dependent on the particle size. With decreasing particle size, ferromagnetic clusters appear on the surface of basically antiferromagnetic particles that result in natural interface and in the appearance of the EB effect. It is shown that the EB effect significantly varies with particle downsizing-basic parameters, for example, exchange-bias field, H EB, and coercive field, H C, are strongly dependent on the particle size. However, variation of these parameters with reduction of particle size may be non-monotonic. One of the characteristic features of the EB systems, the so-called “training effect” (reduction in the strength of the EB effect with increasing number of subsequent hysteresis loops recorded at the same temperature), is discussed. In addition, examples of the EB effect in manganite thin films, heterostructures, nanosheets, and nanowires are reviewed.