Photoinduced ferrimagnetic systems in Prussian blue analogues C(I)xCo4[Fe(CN)6]y (C(I) = alkali cation). 4. Characterization of the ferrimagnetism of the photoinduced metastable state in Rb1.8Co4[Fe(CN)6]3.3-13H2O by K edges X-ray magnetic circular dichroism

In Part 2 of this work, the electronic and local structure of the photoinduced metastable magnetic state of the Prussian blue analogue Rb1.8Co4[Fe(CN)6]3.3-13H2O were characterized. To determine directly the relative orientation of the magnetic moments of Co(II) and Fe(III) ions in the metastable state, and the nature of the exchange interaction between them, we performed X-ray magnetic circular dichroism (XMCD) experiments at the cobalt and iron K edges. We present the first direct experimental evidence of the antiferromagnetic interaction between the cobalt and the iron ions, leading to the ferrimagnetism of the photoinduced metastable state.

Quarter-wave plates and X-ray magnetic circular dichroism on ID24 at the ESRF

The first XMCD measurements carried out on the ID24 energy-dispersive XAS beamline at the ESRF are reported. Circular-polarized X-rays are obtained using perfect diamond crystals as quarter-wave plates. The very small source divergence allows circular polarizations close to unity to be obtained.

Two recent developments in XMCD

This paper reports on two new technical developments concerning sample environments for X-ray magnetic circular dichroism (XMCD). The first measurements under high pressures of up to 30 GPa are described. The difficulties of combining the techniques of high pressure and XMCD are commented on. The second development involves the use of a fast-switching magnetic field. A new superconducting device is used to perform XMCD measurements on paramagnetic compounds in magnetic fields of up to 6 T. The small amplitude of the XMCD signal imposes, for a given signal-to-noise ratio, a noise less than a few 10(-5). The signal-to-noise ratio is improved by the use of a series of acquisitions, switching the magnetic field between each acquisition. A very fast switching mechanism has been built based on mechanical rotation of a superconducting coil, with the sample kept in place inside the coil. The XMCD signals at the L(II,III)-edges of paramagnetic rare-earth compounds have been measured at 4.5 K in fields of up to 6 T with a switching time of 11 s.

Nanosecond-resolved XMCD on ID24 at the ESRF to investigate the element-selective dynamics of magnetization switching of Gd-Co amorphous thin film

The one-bunch filling mode of the ESRF is combined with a microcoil to generate a pulsed-magnetic-field pump phased with respect to the probe that is given by the bunch of photons emitted each turn (357 kHz). Nanosecond-resolved X-ray magnetic circular dichroism (XMCD) is carried out. Besides the microcoil, the two other key-elements are the energy-dispersive XAS spectrometer, which yields parallel data acquisition, and the diamond-based quarter-wave plate, which tunes the helicity of the photon alternatively left and right.