Magnetic materials of strongly correlated origin are at the forefront of research in the exploration of new quantum mechanical properties involving spin and charges. Quantum magnetic materials with certain intrinsic functionalities, such as continuously fluctuating spins to the lowest accessible temperature – reminiscent of a liquid pattern, is argued to form a new phase of matter. Envisaging a phenomenon where the continuously fluctuating spins are also randomly frozen in space can diminish the distinction between the two opposite extremes of quantum and classical magnetism. A team of researchers including MURR scientist Tom Heitmann and led by Prof. Deepak Singh of the MU Department of Physics & Astronomy reports new evidence in this regard where the coexistence of quantum spin continuum with a spin glass order in Co-doped CaRuO₃ perovskite is demonstrated. From experimental characterizations utilizing techniques from heat capacity and magnetic susceptibility to neutron spectroscopy of Co-doped CaRuO₃ perovskite, the team found that (a) a continuum spectrum in the energy-momentum space, due to the uncorrelated spin fluctuations, persists across the weak spin glass transition at T_G ≈ 23 K and (b) the quantum fluctuation of magnetic moment is spatially confined to individual sites only, thereby making it an extremely local event. Thus, the fluctuating spins, at a given time, are also randomly frozen macroscopically. The experimental observations suggest the discovery of a new magnetic phase at the cross-road of classical and quantum physics in strongly correlated perovskite materials.

“Perovskite magnet with quantum mechanical glassiness”, Yiyao Chen, Ashutosh Dahal, Jose Rodriguez-Rivera, Guangyong Xu, Tom Heitmann, Arthur Ernst, and Deepak Singh, Materials Today Physics 12, 100163 (2020).

https://www.sciencedirect.com/science/article/pii/S2542529319301439

The research at MU was supported by the Department of Energy, Office of Science, Office of Basic Energy Sciences under the grant no. DE-SC0014461. This work utilized neutron scattering facilities supported by the Department of Commerce and at the University of Missouri Research Reactor.