14 research outputs found
Stabilization of the high-spin state of Co in LaCoRhO
The rhodium doping in the LaCoRhO perovskite series
() has been studied by X-ray diffraction, electric transport and
magnetization measurements, complemented by electronic structure GGA+U
calculations in supercell for different concentration regimes. No charge
transfer between Co and Rh is evidenced. The diamagnetic ground
state of LaCoO, based on Co in low-spin (LS) state, is disturbed
even by a small doping of Rh. The driving force is the elastic energy connected
with incorporation of a large Rh cation into the matrix of small LS
Co cations, which is relaxed by formation of large Co in
high-spin (HS) state in the next-nearest sites to the inserted Rh atom. With
increasing temperature, the population of Co in HS state increases
through thermal excitation, and a saturated phase is obtained close to room
temperature, consisting of a nearest-neighbor correlation of small (LS
Co) and large (HS Co and LS Rh) cations in a kind of
double perovskite structure. The stabilizing role of elastic and electronic
energy contributions is demonstrated in supercell calculations for dilute Rh
concentration compared to other dopants with various trivalent ionic radius.Comment: 8 pages, 8 figure
A new phenomenon on the surface of FINEMET alloy
This paper is devoted to the analysis of quadratic magneto-optical effects (QMOKE) newly observed at the surface of FINEMET-type Fe73.5Si13.5Nb3Cu1B9 ribbons annealed at temperatures of 733 K and 743 K. A strongly inhomogeneous surface microstructure detected by grazing incident X-ray diffraction (GIXRD), scanning (SEM) and transmission (TEM) electron microscopy is responsible for amplitude and sign changes of the QMOKE in different sample places. Signals in saturation determined by an 8-directional method confirm the prevailing influence of M L M T contributions at some places of a surface and of M2L−M2T at other ones, where M L and M T are in-plane longitudinal and transversal magnetization components. This behavior is explained by random orientation of nanocrystals and/or clusters of the nanometer size (typically units of nm) in the surface layers. The maximal QMOKE magnitude in saturation reaches at some places as much as 0.2 mrad, which is approximately three times lower than the highest contribution observed in Co2FeSi Heusler compounds.Web of Science2641352134