Magnetic structure characterization on 4d5 La2BRhO6 (B = Mg, Zn) materials with double perovskite structure at dilution temperatures with NPD

During the last decade increasing efforts in finding a material realizing the theoretically predicted quantum spin liquid (QSL) state, characterized by the absence of long-ranged magnetic order as well as highly entangled and dynamic spins down to zero Kelvin, has led to intense studies of various frustrated systems. Recently, the search for new QSL compounds has been extended to strongly spin-orbit coupled 4d/5d systems, such as Ir-/Rh-based oxides, showing promising results, motivating to take a closer look also at 4d double perovskites. Here, the relatively understudies Rh4+ 4d5 based compounds La2BRhO6 (B = Zn, Mg) offer an interesting platform for a deeper understanding of the origin of the QSL state. Our preliminary work revealed, that La2ZnRhO6 doesn’t experience any sign of long-range magnetic order down to 0.36 K and a power-law behaviour in specific heat measurements. At the same time magnetisation studies show sizable antiferromagnetic correlation in the high temperature Curie-Weiss behaviour with ΘCW = -36 K resulting in a high frustration factor of 100. An apparent phase transition is only evident in the dilution temperature magnetisation measurements near 1-1.5 K. The thermal hysteretic behaviour and sweep rate dependence suggest a structural origin. Leaving open the possibility of a QSL state. The isostructural La2MgRhO6 on the other hand, having a similar ΘCW, shows signs of an antiferromagnetic phase transition around 7 K.