using neutron diffraction and muon spin spectroscopy*

The transition-metal atoms at B and B’ sites in double perovskite oxide (DPs) having chemical formula A₂BB’O₆ often lead to complex magnetic behaviour and act as a source of intriguing physics. The combined effect of spin, charge and orbital degree of freedom, such as the interaction between the spins at the B/B’ sites, Coulomb interaction, spin-orbit coupling, crystal field effects, etc., give rise to exotic magnetic states. We used neutron diffraction and muon spin spectroscopy techniques [1] together with DC magnetometry and calorimetric measurements to elucidate the magnetic ground state and the origin of a low-temperature anomaly in semiconducting DPs Nd₂FeCrO₆.Structural analysis using X-ray and neutron diffraction techniques confirms the B site-ordered monoclinic phase. While the temperature-dependent neutron diffraction measurement decerns the ferrimagnetic ground state with a net magnetic moment of  ~2μB, arising due to antiferromagnetic interaction between Fe and Cr sub-lattice, muon spin spectroscopy asserts the existence of dynamic long-range commensurate magnetic order below the transition temperature 250 K . Thermal evolution of transverse and longitudinal muon spin relaxation rates reveals that the negative magnetization arises due to the ordering of Nd ion below 20K. Thus, complementary experimental techniques give insight into the microscopic magnetic properties of the system.

References:

 [1] P Dalmas de Réotier and A Yaouanc 1997 J. Phys.: Condens. Matter 9 9113