Giant negative magnetoresistance and kinetic arrest of first-order ferrimagnetic-antiferromagnetic transition in Ge doped Mn_2Sb

摘要

The effect of partial substitution of Ge for Sb on the first-order ferrimagnetic (FRI)-antiferromagnetic (AFM) transition in Mn2Sb has been studied. It shows that the transition temperature (Tt) can be tuned between 119K and 271K by substituting 2.5%-10% Ge at Sb sites in Mn2Sb. The variation of density of state at the Fermi level N(Ef) with Ge substitution shows that dN(E)/dE is positive at EF in the AFM state. With the application of a magnetic field, Tt shifts to low temperature, which results in a giant negative magnetoresistance (MR) reaching a value of 70% for 2.5% substitution. Our results show that FRI to AFM transformation during cooling stops around 35K, even though it remains incomplete. This, along with the nonmonotonic variation of lower critical field, open loop in isothermal MR, and increasing difference in zero field cooled warming and field cooled warming resistivity with increasing magnetic field, shows that the FRI to AFM transition is kinetically arrested in the case of 2.5% Ge substitution.