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arXiv · 1902.08782

The spin-1/2 coupled tetramer system Ba(TiO)Cu$_4$(PO$_4$)$ _4$ probed by magnetization, specific heat, and $^{31}$P-NMR

Vinod Kumar·Aga Shahee·S. Kundu·M. Baenitz·A. V. Mahajan
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Abstract

We present the synthesis and a detailed investigation of structural and magnetic properties of polycrystalline Ba(TiO)Cu$_{4}$(PO$_{4}$)$_{4}$ (BTCPO) via x-ray diffraction, magnetic susceptibility, heat capacity, and $^{31}$P Nuclear Magnetic Resonance (NMR) measurements. BTCPO has a 2D layered structure with interlinked Cu$_{4}$O$_{12}$ tetramer units. A broad maximum is observed around 16.5 K in our magnetization data accompanied by a sharp anomaly around $T$ = 9.5 K in the heat capacity. An anomaly at $T$ = 9.5 K is also found in the temperature dependence of the $^{31}$P NMR spin-lattice relaxation rate $1/T_1$. A power law behavior for the heat capacity as well as for the $^{31}$P $1/T_1$ below the ordering temperature could be obtained. The $^{31}$P NMR lineshape is asymmetric and the NMR shift tracks the bulk spin-susceptibility. We estimated the isotropic and axial components of the hyperfine coupling tensor to be as the $A^{iso}_{hf} \backsimeq 6794$ $\rm{Oe/μ_{B}}$ and $A^{ax}_{hf} \backsimeq 818$ $\rm{Oe/μ_{B}}$, respectively.

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Vinod Kumar, Aga Shahee, S. Kundu, M. Baenitz, A. V. Mahajan. 2019-09-13. The spin-1/2 coupled tetramer system Ba(TiO)Cu$_4$(PO$_4$)$ _4$ probed by magnetization, specific heat, and $^{31}$P-NMR. https://doi.org/10.1016/j.jmmm.2019.165600

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