High temperature magnetic ordering in La2RuO5

Magnetic susceptibility, heat capacity and electrical resistivity measurements have been carried out on a new ruthenate, La2RuO5 (monoclinic, space group P21/c) which reveal that this compound is a magnetic semiconductor with a high magnetic ordering temperature of 170K. The entropy associated with the magnetic transition is 8.3 J/mole-K -close to that expected for the low spin (S=1) state of Ru4+ ions. The low temperatures specific heat coefficient g is found to be nearly zero consistent with the semiconducting nature of the compound. The magnetic ordering temperature of La2RuO5 is comparable to the highest known Curie temperature of another ruthenate, namely, metallic SrRuO3, and in both these compounds the nominal charge state of Ru is 4+.Comment: 16 pages, 6 figures, To be published in Solid State Communication

Magnetocaloric effect in R2Ti3Ge4 (R = Gd, Tb and Er) Compounds

Heat capacity of polycrystalline R2Ti3Ge4 (R = Gd, Tb and Er) compounds (Orthorhombic, Sm5Ge4-type, Space group Pnma) has been studied in the temperature range of 1.8 K to 300 K in various applied magnetic fields. The compounds with magnetic lanthanide elements show interesting low field magnetism intrigued by possible presence of competing antiferromagnetic and ferromagnetic interactions. The magnetocaloric effect in these compounds is estimated from the field dependent heat capacity data. The magnetic entropy change and the adiabatic temperature change in the vicinity of the magnetic transition are found to be significant.Comment: 12 pages incl 3 figures, submitted to Journal of Applied Physic

Magnetoelectricity at room temperature in Bi0.9-xTbxLa0.1FeO3 system

Magnetoelectric compounds with the general formula, Bi0.9-xRxLa0.1FeO3 (R =Gd, Tb, Dy, etc.), have been synthesized. These show the coexistence of ferroelectricity and magnetism, possess high dielectric constant and exhibit magnetoelectric coupling at room temperature. Such materials may be of great significance in basic as well as applied research.Comment: 11 pages of text and figure

Structural and Magnetic Properties of MrSr₂Y₁.₅Ce₀.₅Cu₂Oz (M-1222) Compounds with M = Fe and Co

The MSr2Y1.5Ce0.5Cu2Oz (M-1222) compounds, with M = Fe and Co, have been synthesized through a solid-state reaction route. Both compounds crystallize in a tetragonal structure (space group 14/mmm). A Rietveld structural refinement of the room-temperature neutron diffraction data for Fe-1222 reveals that nearly half the Fe remains at the M site, while the other half goes to the Cu site in the CuO2 planes. Existence of Fe at two different lattice sites is also confirmed by 57Fe Mössbauer spectroscopy from which it is inferred that ~50% of the total Fe occupies the Cu site in the CuO2 planes as Fe3+, whereas the other ~50% is located at the M site with ~40% as Fe4+ and ~10% as Fe3+. For the M[Double Bond]Co compound, nearly 84% of Co remains at its designated M site, while the rest occupies the Cu site in the CuO2 planes

Magnetic and transport properties of Mo substituted La0.67Ba0.33Mn1-xMoxO3 perovskite system

The effect of doping Mo for Mn on the magnetic and transport properties of the colossal magnetoresistance material, La0.67Ba0.33MnO3, has been studied. Compounds of the series La0.67Ba0.33Mn1-xMoxO3 (x=0.0 to 0.1) have been prepared and found to crystallize in the orthorhombic structure (space group Pbnm). Energy Dispersive X-ray Analysis (EDAX) measurements confirm the stoichiometry of all the samples. Magnetotransport and magnetization measurements reveal that the metal-insulator transition temperature (Tp) decreases from 330K for x=0 to 255K for x=0.1. The change in Tp on Mo substitution is relatively much smaller than the corresponding change observed on substitution by other transition elements, such as Ti, Fe, Co, Ni, etc. Further, the ferromagnetic transition temperature (TC) is nearly unchanged by Mo substitution. This is in striking contrast to the large decrease in TC observed with substitution of above-mentioned 3d elements. These unusual magnetic and transport properties of La0.67Ba0.33Mn1-xMoxO3 may be either due to the formation of magnetic pair between Mn and Mo or due to strong Mo(4d)-O(2p) overlap, which in turn, may affect the Mn-Mn interaction via the oxygen atomsComment: 25 pages, 5 figure

Large Second Harmonic Kerr rotation in GaFeO3 thin films on YSZ buffered Silicon

Epitaxial thin films of gallium iron oxide (GaFeO3) are grown on (001) silicon by pulsed laser deposition (PLD) using yttrium-stabilized zirconia (YSZ) buffer layer. The crystalline template buffer layer is in-situ PLD grown through the step of high temperature stripping of the intrinsic silicon surface oxide. The X-ray diffraction pattern shows c-axis orientation of YSZ and b-axis orientation of GaFeO3 on Si (100) substrate. The ferromagnetic transition temperature (TC ~ 215 K) is in good agreement with the bulk data. The films show a large nonlinear second harmonic Kerr rotation of ~15 degrees in the ferromagnetic state.Comment: 16 pages, 4 figures, To be published in J. Magn. Magn. Ma