To study the thermoelectric properties of SrTiO 3 doped with lanthanum and dysprosium, ceramic samples were prepared using the conventional solid-state reaction method. The total doping amount was fixed at 20 mol% with different amounts of lanthanum and dysprosium contents. The X-ray diffraction pattern suggests that the main crystal structure is cubic perovskite with a small amount of the second phase of Dy 2 Ti 2 O 7 . Scanning electronic microscope surface morphology images revealed that the ceramic samples consisted of homogeneous grains with an average grain size of 4.1-6.2 lm. The electrical conduction of the samples as a function of temperature had similar behavior to that of metallic conductivity. The Seebeck coefficients were negative, which indicates that electrons were the dominant carriers. As the dysprosium content increased, both the electrical conductivity and thermal conductivity decreased; in contrast, the absolute value of the Seebeck coefficient increased. The power factor reached 1318 lW/K 2 m at 570 K with 12% dysprosium and 8% lanthanum doped in SrTiO 3 . The lowest thermal conductivity was 2.3 W/mK for the sample with 20% dysprosium as a dopant. The maximum figure of merit (ZT) of 0.36 at 1076 K was obtained for SrTiO 3 doped with 12% dysprosium and 8% lanthanum, which is a result of the high power factor combined with low thermal conductivity.

Ti O 2 -based magnetic semiconductors with high Co doping concentrations (Ti1−xCoxO2) were synthesized under thermal nonequilibrium condition by sputtering machine. Microstructure and composition analysis by transmission electron microscopy, x-ray photoelectron spectroscopy, and electron energy-loss spectroscopy indicated that Co element was incorporated into TiO2 to form Ti1−xCoxO2 compound. The direct evidence for the compositional inhomogeneity of the Ti1−xCoxO2 compound was given. Room temperature ferromagnetism with high magnetization was obtained, which could be attributed to the intrinsic properties of the amorphous magnetic semiconductor. The electrical transport in a low temperature range was explained by spin-dependent Efros’s variable range hopping, and correspondingly an exponential function of the magnetoresistance versus T−1∕2 was found.

We report electric field control of the interfacial Dzyaloshinskii-Moriya interaction (DMI) in MgO/Fe/Pt multilayers. The interfacial DMI is obtained and quantified by Brillouin light scattering measurements based on the frequency nonreciprocity of spin waves in a ferromagnet. The magnitude of the induced DMI is found to linearly increase as a function of electric field intensity. The efficiency of electric field control of the interfacial DMI characterized as a ratio of the DMI energy change to the electric field, which is found to be equal to 67 fJ/(Vm) with a positive electric field. We further demonstrate that the origin of the enhanced DMI results from the MgO/Fe interface. The Rashba spin-orbit coupling and electric field induced anisotropy at the MgO/Fe interface might be responsible for the enhanced interfacial DMI. Our findings open up a way for exploring the spintronic devices with a tunable DMI.

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First principles calculations are employed to investigate both type I and II silicon clathrates. The phonon and infrared spectra of both types of clathrate are obtained. We find a localized vibrational mode of Si46 whose frequency is 375.0 cm−1, where the vibration in the mode localizes in the hexagonal chain. The heat capacity of both clathrates is the same as that of the diamond phase Si (d-Si). When the temperature is lower than 100 K, the Debye temperatures of the clathrates are higher than that of d-Si; however, the Debye temperatures of both clathrates at high temperature (>100 K) are lower than that of the d-Si. The mean free paths (λ) and thermal conductivities (κ) of the clathrates are larger than those of d-Si at low temperature. The Seebeck coefficients (S) of the clathrates are higher than that of d-Si in the temperature interval 300–1000 K; however, both clathrates exhibit a lower value of σ/τ when compared to the d-Si.