Unveiling the magnetic structure and phase transition of Cr2CoAl using neutron diffraction

Abstract

We report the detailed analysis of temperature dependent neutron diffraction pattern of the Cr2CoAl inverse Heusler alloy and unveil the magnetic structure up to the phase transition as well as its fully compensated ferrimagnetic nature. The Rietveld refinement of the diffraction pattern using the space group I4¯m2 confirms the inverse tetragonal structure over the large temperature range from 100 to 900 K. The refinement of the magnetic phase considering the wave vector k= (0, 0, 0) reveals the ferrimagnetic nature of the sample below 730±5 K. This transition temperature is obtained from empirical power law fitting of the variation in the ordered net magnetic moment variation in intensity of (110) peak as a function of temperature. The spin configuration of the microscopic magnetic structure suggests the nearly fully compensated ferrimagnetic behavior where the magnetic moments of Cr2 are antiparallel with respect to the Cr1 and Co moments. Moreover, the observed anomaly in the thermal expansion and lattice parameters at 730±5 K suggests that the distortion in the crystal structure may play an important role in the magnetic phase transition.