• Baines, C.
• Sarkar, R.
• Grinenko, Vadim
• Klauss, H. H.
• Andrade, E. C.
• Bräuninger, S.
• Freitas, R. S.
• Garcia, F. A.
• Luetkens, H.
• Araújo, J. C. R.
• Lora-Serrano, R.
• Amaral, R. P.
• Cantarino, M. R.

Abstract

Magnetic frustration and disorder are key ingredients to prevent the onset of magnetic order. In the disordered hexagonal double perovskite BaTi$_{1/2}$Mn$_{1/2}$O$_{3}$, Mn$^{4+}$ cations, with $S=3/2$ spins, can either form highly correlated states of magnetic trimers or dimers or remain as weakly interacting orphan spins. At low temperature ($T$), the dimer response is negligible, and magnetism is dominated by the trimers and orphans. To explore the role of magnetic frustration, disorder and possibly of quantum fluctuations, the low-$T$ magnetic properties of the remaining magnetic degrees of freedom of BaTi$_{1/2}$Mn$_{1/2}$O$_{3}$ are investigated. Heat-capacity data and magnetic susceptibility display no evidence for a phase transition to a magnetically ordered phase but indicate the formation of a correlated spin state. The low-temperature spin dynamics of this state is then explored by SR experiments. The zero field $^{+}$ relaxation rate data show no static magnetism down to $T=19$ mK and longitudinal field experiments support as well that dynamic magnetism persists at low $T$. Our results are interpreted in terms of a spin glass state which stems from a disordered lattice of orphans spins and trimers. A spin liquid state in BaTi$_{1/2}$Mn$_{1/2}$O$_{3}$, however, is not excluded and is also discussed. ; Comment: Main Text: 6 pages, 4 figures; Supplemental: 11 pages, 7 figures

Topics

• perovskite
• impedance spectroscopy
• experiment
• glass
• glass
• phase transition
• susceptibility
• ordered phase