The influence of hydrogen pressure on the magnetic and microstructure properties of Zr2(Co0.5Fe0.2Ni0.2V0.1) alloy was investigated in low and high hydrogen pressure. XRD and Rietveld refinement analysis of the as- cast alloy shows a multiphase crystal structure, mainly consisting of the C16 tetragonal phase. Mossbauer spectra and magnetic measurements confirmed a formation of interacting superparamagnetic clusters within a paramagnetic matrix. A typical spin glass-like transition was observed at blocking temperature below 30 K. Hydrogenation shows a significant increase in the magnetic properties. Under low hydrogen pressure (hydrogen content ¡­19 mmol/gr), a ferromagnetic hysteresis loop was observed without any significant change in the crystal structure, indicating that exchange interaction between clusters increased markedly by hydrogenation. In high hydrogen pressure (hydrogen content ¡­42 mmol/gr), the disproportionation reaction altered both the crystal structure and the magnetic property of the alloy. The presence of at least two interacting superparamagnetic phases within the paramagnetic matrix can be represented by fitting the M(H) data to the theoretical model. This study discusses a complex case of magnetic clusters embedded in a paramagnetic matrix and is a good example of drastic changes of magnetic properties by hydrogenation.

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