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Enhanced electrical resistance at the field-induced magnetic transitions in some stoichiometric and nonstoichiometric Tb-based ternary germanides

We present the magnetic and transport behavior of some Tb compounds, viz., TbIrGe2, TbFe(0.4)Ge2, and TbCo(0.4)Ge2. The stoichoometric germanide TbIrGe2 exhibits at least two distinct magnetic transitions in a close temperature interval around 10 K. The non-stoichiometric compounds, TbFe(0.4)Ge2 and TbCo(0.4)Ge2, undergo magnetic ordering around 17 and 19 K respectively. The magnetic state of these compouds appears to be antiferromagnetic-like. Qualitatively, there is a correlation between the field response of the magnetization (M), the magnetoresistance (MR) and the entropy change curve in all these compouds. That is, these Tb compounds exhibit a "positive" MR and entropy change beyond a magnetic field where M also shows a field-induced transition. On the basis of this correlaion, we conclude that magnetic disorder/fluctuations beyond a critical field - "a phenomenon called inverse metamagnetism" - rather than metamagnetism,is induced in these compounds.