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Novel thermal effects across first order magnetic transition in Ta doped $HfFe_2$ intermetallic

Novel thermal effects across the first order antiferromagnetic (AFM) - ferromagnetic (FM) transition in an intermetallic alloy are reported. They show instances of warming when heat is extracted from the sample, and cooling when heat is provided to the sample across AFM-FM transition in Ta doped $HfFe_2$, thus providing indisputable evidence of metastable supercooled AFM and superheated FM states, respectively. Such thermal effects in a magnetic solid prepared from commercially available materials has been reported for the first time. The transition proceeds in multiple steps which is interpreted in the framework of quenched disorder broadening of AFM-FM transition and classical nucleation theory. Measurements in the presence of magnetic field conform to above frame work.