Rohit Singh, Saurabh Kumar Srivastava, Arun K. Nigam, Vladimir V. Khovaylo, Lajos K. Varga, Ratnamala Chatterjee
In this work we demonstrate that polycrystalline ribbons of (Ni48Co6)Mn26Al20 with a B2 structure at room temperature shows a multi-component magnetic behavior with frozen disorders at low temperatures. (Ni48Co6)Mn26Al20 goes through a magnetic phase transition at ~ 200 K that mimics ferro to para like transition. Deduced from the Arrott plots the Neel temperature of (Ni48Co6)Mn26Al20 is ~170 K. Based on Neel theory, a cluster model is used to explain the presence of ferromagnetic and antiferromagnetic clusters in the studied ribbons. Formation of ferromagnetic clusters can be understood in terms of positive exchange interactions among the Mn atoms that are neighboring to Co atoms which are located on the Ni sites. Competing positive and negative exchange interactions are evident from a non-saturating high field magnetization and initial steep rise in M-H curves. Large high-field susceptibility of the austenitic phase, hysteresis of the magnetization appearing in strong magnetic fields in the vicinity of Curie temperature Tc, and a broad ferromagnetic to paramagnetic transition are ascribed to the nanoscaled compositional inhomogeneities of the ribbons. We confirm the presence of competing exchange interactions in the sample.
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http://arxiv.org/abs/1305.6255
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