2,462 research outputs found
NMR study on the stability of the magnetic ground state in MnCrO
The canting angles and fluctuation of the magnetic ion spins of spinel oxide
MnCrO were studied by nuclear magnetic resonance (NMR) at low
temperatures, which has a collinear ferrimagnetic order below and a
ferrimagnetic spiral order below . Contrary to previous reports,
only one spin canting angle of Cr ions was observed. The spin canting angles of
Mn and Cr ions in the ferrimagnetic spiral obtained at a liquid-He temperature
were 43\,^{\circ} and 110\,^{\circ}, respectively. The nuclear spin-spin
relaxation was determined by the Suhl-Nakamura interaction at low temperatures
but the relaxation rate increases rapidly as the temperature
approaches . This indicates that the fluctuation of the spiral component
becomes faster as the temperature increases but not fast enough to leave an
averaged hyperfine field to nuclei in the time scale of nuclear spin precession
in the ferrimagnetic phase, which is on the order of s. The spiral
volume fraction measured for various temperatures reveals that the collinear
and the spiral ferrimagnetic phases are mixed below the transition temperature
of the spiral order. The temperature hysteresis in the volume fraction implies
that this transition has first-order characteristics.Comment: 13 pages, 5 figure
Gating of memory encoding of time-delayed cross-frequency MEG networks revealed by graph filtration based on persistent homology
To explain gating of memory encoding, magnetoencephalography (MEG) was analyzed over multi-regional network of negative correlations between alpha band power during cue (cue-alpha) and gamma band power during item presentation (item-gamma) in Remember (R) and No-remember (NR) condition. Persistent homology with graph filtration on alpha-gamma correlation disclosed topological invariants to explain memory gating. Instruction compliance (R-hits minus NR-hits) was significantly related to negative coupling between the left superior occipital (cue-alpha) and the left dorsolateral superior frontal gyri (item-gamma) on permutation test, where the coupling was stronger in R than NR. In good memory performers (R-hits minus false alarm), the coupling was stronger in R than NR between the right posterior cingulate (cue-alpha) and the left fusiform gyri (item-gamma). Gating of memory encoding was dictated by inter-regional negative alpha-gamma coupling. Our graph filtration over MEG network revealed these inter-regional time-delayed cross-frequency connectivity serve gating of memory encoding
- β¦