The study of negative thermal expansion and magnetic evolution in antiperovskite compounds Cu0.8-xSnxMn0.2NMn3(0 ≤ x ≤ 0.3)

With increasing the substitution of Sn for Cu in Cu0.8-xSnxMn0.2NMn3, the initial cubic-tetragonal structural phase transition disappears for the samples x >= 0.10 and is replaced by a discontinuous lattice expansion with a cubic structure which has been confirmed by the measurements of variable temperature x-ray diffractions and specific heat. The discontinuous lattice expansion broadens with increasing the doping level x and the negative thermal expansion coefficient up to -64.54 ppm/K between 190 K and 235 K is found for the sample x = 0.3. Detailed magnetic measurements indicate that the magnetic ground state is meta-stable for the lower-doping level and transforms into spin-glass-like state owing to the enhancement of antiferromagnetic interaction when x is up to 0.3. Furthermore, the magnetization curves M(T) display abnormal behaviors for lower-x. For the samples x = 0.1 and 0.2, the jump of field-cooled magnetization curve M-FC (defined as Delta M-FC/M-FC) around the lower-temperature magnetic transition is suppressed with increasing the magnetic field. These abnormalities of magnetizations are also discussed based on a simple model. (C) 2012 American Institute of Physics. [doi:10.1063/1.3684653]