Temperature dependent orbital degree of freedom in a bilayer manganite by magnetic Compton scattering

We have measured temperature-dependent magnetic Compton profiles (MCPs) from a single crystal of La$_{1.2}$Sr$_{1.8}$Mn$_2$O$_7$. The MCPs, which involved the scattering of circularly polarized x-rays, are in general related to the momentum density of all the unpaired spins in the system. Nevertheless, we show that when the x-ray scattering vector lies along the [110] direction, the number of magnetic electrons of a specific symmetry, i.e. $d$-electrons of $x^2-y^2$ symmetry, yield a distinct signature in the MCP, allowing us to monitor substantial changes in the occupancy of the $d_{x^2-y^2}$ states over the investigated temperature range of 5-200K. This study indicates that magnetic Compton scattering can provide a powerful window on the properties of specific magnetic electrons in complex materials.Comment: 5 pages, 4 figures, to appear in Phys. Rev. Let

Spin moment over 10-300 K and delocalization of magnetic electrons above the Verwey transition in magnetite

In order to probe the magnetic ground state, we have carried out temperature dependent magnetic Compton scattering experiments on an oriented single crystal of magnetite (Fe$_3$O$_4$), together with the corresponding first-principles band theory computations to gain insight into the measurements. An accurate value of the magnetic moment $\mu_S$ associated with unpaired spins is obtained directly over the temperature range of 10-300K. $\mu_S$ is found to be non-integral and to display an anomalous behavior with the direction of the external magnetic field near the Verwey transition. These results reveal how the magnetic properties enter the Verwey energy scale via spin-orbit coupling and the geometrical frustration of the spinel structure, even though the Curie temperature of magnetite is in excess of 800 K. The anisotropy of the magnetic Compton profiles increases through the Verwey temperature $T_v$ and indicates that magnetic electrons in the ground state of magnetite become delocalized on Fe B-sites above $T_v$.Comment: 5 pages, 5 figures, to appear in Journal of Physics and Chemistry of Solid

X-Ray Magnetic Circular Dichroism of Pulsed Laser Deposited Co2MnSn and Co2MnSb Thin Films Grown on GaAs (001)

We present the structural and element specific magnetic properties of Co2MnSn and Co2MnSb thin films grown on GaAs (100) substrates using pulsed laser deposition. X-ray magnetic circular dichroism (XMCD) spectra were measured for 400 A thick films at the L2,3 edges of Co and Mn. Element specific moments for Co and Mn in Co2MnSn were calculated from the x-ray absorption and XMCD spectra using the XMCD sum rules. The ratios of orbital to spin magnetic moments for Co and Mn were calculated for Co2MnSn and Co2MnSb

Magnetic Compton scattering study on highly correlated electronic systems.

Magnetic Compton scattering study on highly correlated electronic systems