Effect of pressure on the electronic and magnetic properties of CdV2_2O4_4: Density functional theory studies

We investigate the effect of pressure on the electronic and magnetic states of CdV$_2$O$_4$ by using ab initio electronic structure calculations. The Coulomb correlation and spin-orbit coupling play important role in deciding the structural, electronic and magnetic properties of the compound. The total magnetic moment of V ion is found to be $\sim$1.3 $\mu_B$ and making an angle of $\sim$9.5 degree with the z-axis. In the tetragonal phase, the ground state is the orbital ordered state where V $d_{xz}$ and $d_{yz}$ obtitals are mainly occupied at the neighbouring sites. This work predicts the electronic phase transition from orbital-ordered-insulator to orbital-ordered-metal to orbital-disordered-metal with increasing pressure. The pressure induced broadening of lower and upper Hubbard bands gives rise to metal-insulator transition above 35 GPa. The simple mean-field theory used in the present work is able to describe the pressure dependent variation of the antiferromagnetic transition temperature suggesting the applicability of the method in the study of the magnetic behaviour of similar geometrically frustrated systems.Comment: 12 pages, 7 figures, to appear in Phys. Rev.

Automated Instrumentation for the Determination of the High-Temperature Thermoelectric Figure-of-Merit

In this work, we report the fabrication of a high temperature measurement setup to measure Figure of merit (ZT). This setup facilitates the simultaneous measurement of Seebeck coefficient ({\alpha}), thermal conductivity (\kappa), and electrical resistivity (\rho) required to calculate ZT. Measurement of temperature, as well as voltages using same thermocouples, simplified the design of the setup by minimizing sensors and wires. Limited components used in the sample holder further simplify the design and make it small in size and lightweight. The dedicated thin heater is made, which minimizes the heat loss. Further, low heat loss is achieved by optimizing the insulator dimension. To measure power delivered to the heater, 4-wire technique is used. Low cost and commonly available materials used in the fabrication of various components make it more accessible to the user as any parts can be easily replaced in case of any damage occurs. A dedicated program is built in the Python programming language to automate the whole measurement process. p-type Bi0.36Sb1.45Te3 sample is used to calibrate this measurement setup. The data collected are found to be in good agreement with the reported data.Comment: 14 pages, 8 figure