Although abundant research has focused recently on the quantum criticality of itinerant magnets, critical phenomena of insulating magnets in the vicinity of critical endpoints (CEPs) have rarely been revealed. Here we observe an emergent CEP at 2.05
T and 2.2 K with a suppressed thermal conductivity and concomitant strong critical fluctuations evident via a divergent magnetic susceptibility (e.g., chi(2.05 T, 2.2 K)/chi(3 T, 2.2 K)=23,500 %, comparable to the critical opalescence in water) in the hexagonal insulating antiferromagnet HoMnO3.
Near-Earth asteroid 162173 (1999 JU3) is a potential target of two asteroid sample return missions, not only because of its accessibility but also because of the first C-type asteroid for exploration missions. The lightcurve-related physical properti
es of this object were investigated during the 2011-2012 apparition. We aim to confirm the physical parameters useful for JAXAs Hayabusa 2 mission, such as rotational period, absolute magnitude, and phase function. Our data complement previous studies that did not cover low phase angles. With optical imagers and 1-2 m class telescopes, we acquired the photometric data at different phase angles. We independently derived the rotational lightcurve and the phase curve of the asteroid. We have analyzed the lightcurve of 162173 (1999 JU3), and derived a synodic rotational period of 7.625 +/- 0.003 h, the axis ratio a/b = 1.12. The absolute magnitude H_R = 18.69 +/- 0.07 mag and the phase slope of G = -0.09 +/- 0.03 were also obtained based on the observations made during the 2011-2012 apparition.
We report neutron diffraction and magnetization studies of the magnetic order in multiferroic BiFeO3. In ferroelectric monodomain single crystals, there are three magnetic cycloidal domains with propagation vectors equivalent by crystallographic symm
etry. The cycloid period slowly grows with increasing temperature. The magnetic domain populations do not change with temperature except in the close vicinity of the N{P}eel temperature, at which, in addition, a small jump in magneti- zation is observed. No evidence for the spin-reorientation transitions proposed in previous Raman and dielectric studies is found. The magnetic cycloid is slightly anharmonic for T=5 K. The an- harmonicity is much smaller than previously reported in NMR studies. At room temperature, a circular cycloid is observed, within errors. We argue that the observed anharmonicity provides important clues for understanding electromagnons in BiFeO3.
