Giant room-temperature spontaneous exchange bias in antiferromagnet Fe3BO6 polycrystals

What is it about?

A giant spontaneous exchange bias (SEB) effect in antiferromagnetic Fe3BO6 polycrystals, which is prepared by using nanoscale raw materials. The value of the spontaneous exchange bias field at room temperature is as large as about 4234 Oe. The room-temperature training effect, temperature-dependence, and maximum field-dependence of the were investigated. We propose that this giant SEB originates from the exchange-coupling interactions between the weak ferromagnetic surface state and the bulk antiferromagnetic state. The theoretical analysis results were further verified by comparing the magnetic properties of the Fe3BO6 with relatively low crystallinity.

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Why is it important?

Different from conventional exchange bias, spontaneous exchange bias (SEB) effect is observed by the process of zero-field cooling from higher temperatures in the unmagnetized Ni-Mn-In alloy by Wang et al. From the perspective of practical applications, obtaining a large SEB at room temperature has a higher application value. Fe3BO6 is an AFM material composed of only Fe3+(3d5) spins, and its Nèel temperature is as high as approximately 508 K. It has wide application prospects in power energy, biology, pharmaceutical compounds, and catalysis of electric and hybrid vehicles. If a large room-temperature SEB is achieved in this material, it will be better extended to other application areas and provide a candidate material for devices based on the SEB effect.

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