energy materials and nanotechnology, Donostia, İspanya, 1 - 04 Eylül 2015, ss.20
Investigation of the relation between hysteresis and ferromagnetism in Mn3GaC
Ö. Çakır,1 M. Acet,2 M. Farle,2 A. Senyshyn,3
1Physics Department, Yildiz Technical University, Istanbul, Turkey
2Faculty of Physics, Duisburg-Essen University, D-47048 Duisburg,Germany
3Forschungsneutronenquelle Heinz Maier-Leibnitz FRM-II, Technische Universitat Munchen,
Mn3GaC among the Mn-based Antipervoskite compounds shows a first order magnetostructural transition from the antiferromagnetic state (AF) to ferromagnetic state (FM) with increasing temperature at Tt = 165 K accompanied with volume change. A thermal hysteresis of 3 KT-1 occurs at the transition. To decrease the thermal hysteresis, we have substituted 15 % of nitrogen in place of carbon. As a result, long range ferromagnetism disappeared along with the thermal hysteresis. To understand the source of the thermal hysteresis and its relation with ferromagnetism, we have undertaken neutron diffraction and neutron depolarization experiments on the Mn3GaC and Mn3Ga(C0.85N0.15). According to the results of neutron diffraction experiments for Mn3GaC, the (332) nuclear reflection shows that at the transition lattice constants associated with both the AF and the FM phase coexist indicating that the system is in a heavily strained state, which can be a cause for the hysteresis. In the neutron depolarization experiments on Mn3Ga(C0.85N0.15), the flipping ratio does not change when crossing the transition showing the absence of ferromagnetic domains around the first order transition. One factor which leads to narrow hysteresis at magnetostructural transitions is the absence of long-range ferromagnetism in the parent phase of the material.