The irreversible structural change in Mn1.1Fe0.9P0.8Ge0.2: Evidence for a magnetic driver

Neutron powder diffraction measurements complemented by first-principles density functional theory (DFT) calculations have been used to study the irreversible change that accompanies the reversible magnetocaloric transition (MCT) in Mn1.1Fe0.9P0.8Ge0.2. We observe the growth and loss of long-period antiferromagnetism as we pass through the MCT for the first time and the development of significant strain in the cycled material. We attribute both the reversible and irreversible changes to the distance dependence of the Mn-Mn exchange in the Mn-P(Ge) ab-plane layers. (C) 2016 Author(s).