Single crystals of CeGe and its non-magnetic analogue LaGe have been grown by Czochralski method. CeGe compound crystallizes in the orthorhombic FeB-type crystal structure with the space group textit{Pnma} (#62). The anisotropic magnetic properties h
ave been investigated on well oriented single crystals by measuring the magnetic susceptibility, electrical resistivity and heat capacity. It has been found that CeGe orders antiferromagnetically at 10.5 K. Both transport and magnetic studies have revealed large anisotropy reflecting the orthorhombic crystal structure. The magnetization measurement measured at 2 K revealed metamagnetic transitions along the [010] direction at 4.8 and 6.4 T and along [100] direction at a critical field of 10.7 T, while the magnetiztaion along [001] direction was increasing linearly without any anomaly up to a field of 16 T. From the magnetic susceptibility and the magnetization measurements it has been found that [010] direction is the easy axis of magnetization. The electrical resistivity along the three crystallographic directions exhibited an upturn at $T_{rm N}$ indicating the superzone gap formation below $T_{rm N}$ in this compound. We have performed the crystalline electric field (CEF) analysis on the magnetic susceptibility and the heat capacity data and found that the ground state is doublet and the splitting energies from the ground state to the first and second excited doublet states were estimated to be 39 and 111 K, respectively.
Here we report the structural, electrical and magnetic properties of Fe doped La0.7Ca0.3Mn1-xFexO3 with x = 0.0 to 1.0 prepared by conventional solid state reaction method. Simulated data on XRD shows an increase in volume with an increase in Fe ion
concentration. XPS supports that Fe3+ ions directly substitute Mn3+ ions. Shifting towards lower wave-number and symmetric IR band structure confirms increase in volume and homogeneous distribution of Fe ions. Fe ion doesnt contribute in double-exchange (DE) conduction mechanism due to its stable half filled 3d orbital. The presence of Fe3+ ions encourages anti-ferromagnetism (AFM) generated by super-exchange interaction and suppress insulator-metal transition temperature (TIM). Magnetic measurements show the existence of magnetic polarons supported by increase in volume of unit cell and deviation from Curie-Weiss law.
Here we report the optimized magneto-transport properties of polycrystalline La0.70Ca0.3-xSrxMnO3 and their composites with Ag. The optimization was carried out by varying the Sr and Ag contents simultaneously to achieve large temperature coefficient
of resistance (TCR) as well as low field magneto-resistance (MR) at room temperature. Sharpest paramagnetic (PM)-ferromagnetic (FM) and insulator-metal (IM) transition is observed in the vicinity of the room temperature (TC=300 K=TIM) for the composition La0.70Ca0.20Sr00.10MnO3:Ag0.20. Partial substitution of larger Sr2+ ions at the Ca2+ ions sites controls the magnitude of the FM and IM transition temperatures, while the Ag induces the desired sharpness in these transitions. For the optimized composition, maximum TCR and MR are tuned to room temperature (300 K) with the former being as high as 9% and the later being 20 and 30 percent at 5 and 10 kOe magnetic fields respectively. Such sharp single peak (TCR= 9 percent) at room temperature can be used for the bolometric and infrared detector applications. The achievement of large TCR and low field MR at T~300K in polycrystalline samples is encouraging and we believe that further improvements can be achieved in thin films, which, by virtue of their low conduction noise, are more suitable for device applications.
We report anisotropic dc magnetic susceptibility $chi(T)$, electrical resistivity $rho(T)$, and heat capacity $C(T)$ measurements on the single crystals of CaFe$_{2-x}$Co$_x$As$_2$ for $x$ = 0 and 0.06. Large sized single crystals were grown by the h
igh temperature solution method with Sn as the solvent. For the pure compound with $x$ = 0, a high temperature transition at 170 K is observed which is attributed to a combined spin density wave (SDW) ordering and a structural phase transition. On the other hand, for the Co-doped samples for $x$ = 0.06, the SDW transition is suppressed while superconductivity is observed at $simeq$17 K. The superconducting transition has been confirmed from the magnetization and electrical resistivity studies. The $^{57}$Fe Mossbauer spectrum in CaFe$_2$As$_2$ indicates that the SDW ordering is incommensurate. In the Co-doped sample, a prominent paramagnetic line at 4.2 K is observed indicating a weakening of the SDW state.
