We investigate magnetic, thermal, and dielectric properties of SrCuTe2O6, which is isostructural to PbCuTe2O6, a recently found, Cu-based 3D frustrated magnet with a corner sharing triangular spin network having dominant first and second nearest neig
hbor (nn) couplings [B. Koteswararao, et al. Phys. Rev. B 90, 035141 (2014)]. Although SrCuTe2O6 has a structurally similar spin network, but the magnetic data exhibit the characteristic features of a typical quasi -one-dimensional magnet, which mainly resulted from the magnetically dominant third nn coupling, uniform chains. The magnetic properties of this system are studied via magnetization (M), heat capacity (Cp), dielectric constant, measurements along with ab-initio band structure calculations. Magnetic susceptibility chi(T) data show a broad maximum at 32 K and the system orders at low temperatures TN1=5.5 K and TN2=4.5 K, respectively. The analysis of chi(T) data gives an intra-chain coupling, J3/kB, to be about - 42 K with non-negligible frustrated inter-chain couplings (J1/kB and J2/kB). The hopping parameters obtained from LDA band structure calculations also suggest the presence of coupled uniform chains. The observation of simultaneous anomalies in dielectric constant at TN1 and TN2 suggests the presence of magneto-dielectric effect in SrCuTe2O6. A magnetic phase diagram is also built based on M, C p, and dielectric constant results.
We have investigated the magnetic properties of Mn and Cu substituted SrZnO2 single crystals (SrZn0.99Mn0.01O2 and SrZn0.99Cu0.01O2). We observed signatures of weak ferromagnetism as a sharp increase of magnetic susceptibility below 5 K even in the l
ow percentage (x= 0.01) of Mn substituted single crystals. Magnetic susceptibility data measured parallel or perpendicular to the ab plane yield anisotropic behavior with Curie Weiss temperature of about -320 K and -410 K, respectively, suggesting the presence of strong antiferromagnetic couplings among Mn atoms at high temperatures, similar to the Mn doped ZnO and Fe doped BaTiO3 samples. In contrast, the SrZn0.99Cu0.01O2 crystal shows paramagnetic behavior down to 2 K.
We report magnetic susceptibility (chi) and heat capacity Cp measurements along with ab-initio electronic structure calculations on PbCuTe2O6, a compound made up of a three dimensional 3D network of corner-shared triangular units. The presence of ant
iferromagnetic interactions is inferred from a Curie-Weiss temperature (theta_CW) of about -22 K from the chi(T) data. The magnetic heat capacity (Cm) data show a broad maximum at T^max ~ 1.15 K (i.e. T^max/theta_CW ~ 0.05), which is analogous to the the observed broad maximum in the Cm/T data of a hyper-Kagome system, Na4Ir3O8. In addition, Cm data exhibit a weak kink at T^* ~ 0.87 K. While the T^max is nearly unchanged, the T^* is systematically suppressed in an increasing magnetic field (H) up to 80 kOe. For H > 80 kOe, the Cm data at low temperatures exhibit a characteristic power-law (T^{alpha}) behavior with an exponent {alpha} slightly less than 2. Hopping integrals obtained from the electronic structure calculations show the presence of strongly frustrated 3D spin interactions along with non-negligible unfrustrated couplings. Our results suggest that PbCuTe2O6 is a candidate material for realizing a 3D quantum spin liquid state at high magnetic fields.
We report the synthesis and characterization of Li2ZnV3O8, which is a new Zn-doped LiV2O4 system containing only tetravalent vanadium. A Curie-Weiss susceptibility with a Curie-Weiss temperature of <theta>CW ~214 K suggests the presence of strong ant
iferromagnetic correlations in this system. We have observed a splitting between the zero-field cooled ZFC and field cooled FC susceptibility curves below 6 K. A peak is present in the ZFC curve around 3.5 K suggestive of spin-freezing . Similarly, a broad hump is also seen in the inferred magnetic heat capacity around 9 K. The consequent entropy change is only about 8% of the value expected for an ordered S = 1=2 system. This reduction indicates continued presence of large disorder in the system in spite of the large <theta>CW, which might result from strong geometric frustration in the system. We did not find any temperature T dependence in our 7Li nuclear magnetic resonance NMR shift down to 6 K (an abrupt change in the shift takes place below 6 K) though considerable T-dependence has been found in literature for LiV2O4- undoped or with other Zn/Ti contents. Consistent with the above observation, the 7Li nuclear spin-lattice relaxation rate 1/T1 is relatively small and nearly T-independent except a small increase close to the freezing temperature, once again, small compared to undoped or 10% Zn or 20% Ti-doped LiV2O4.
We present magnetic suscceptibility and heat capacity data on a new S=1/2 two-leg spin ladder compound BiCu2PO6. From our susceptibility analysis, we find that the leg coupling J1/k_B is ~ 80 K and the ratio of the rung to leg coupling J2/J1 ~ 0.9. W
e present the magnetic contribution to the heat capacity of a two-leg ladder. The spin-gap Delta/k_B =3 4 K obtained from the heat capacity agrees very well with that obtained from the magnetic susceptibility. Significant inter-ladder coupling is suggested from the susceptibility analysis. The hopping integrals determined using Nth order muffin tin orbital (NMTO) based downfolding method lead to ratios of various exchange couplings in agreement with our experimental data. Based on our band structure analysis, we find the inter-ladder coupling in the bc-plane J2 to be about 0.75J1 placing the compound presumably close to the quantum critical limit.
