Investigation of Novel Properties in Ludwigites

Abstract

Ludwigites are a class of oxyborates with the chemical formula M2(II)M'(III)O2BO3 where M and M' are metal ions. These materials have been widely studied because of its three leg ladder structure and spin and charge ordering along these triads. Due to their interesting properties like charge ordering and weak ferromagnetism, they are also potential candidates for multiferroicity. This project aims to investigate the structural, magnetic, dielectric and specific heat properties of some newly synthesized ludwigite systems. During this project two of the rarely studied ludwigites Ni2AlO2BO3 and Co2AlO2BO3 were synthesized using flux growth, with borax as the flux. Both of these compounds have orthorhombic crystal structure, with space group symmetry Pbam. Magnetic measurements showed antiferromagnetic ordering at 38K and 36K for Ni2AlO2BO3 and Co2AlO2BO3 respectively. There also appears to be a first order transition in Co2AlO2BO3 at 50K. Magnetization and specific heat vs. Field measurements at different temperatures showed metamagnetic transitions for both of these samples. The possibility of magnetodielectric effect has been observed in dielectric measurements done for Ni2AlO2BO3 which is indicated by a sharp jump in the dielectric constant at the magnetic transition temperature. Specific heat measurements showed large magnetocaloric effect (MCE) in both Ni2AlO2BO3 and Co2AlO2BO3 with MCE in Co2AlO2BO3 being two times higher than that in Ni2AlO2BO3.