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The A(1), E(1) and E(2) Raman active modes in hexagonal YMnO(3) and LuMnO(3) single crystals are studied as a function of temperature and compared with previous measurements. In addition to anharmonicity, some phonon frequencies show below T(N) anomalous temperature dependences that reflect the atomic displacements while some other phonon frequencies are more sensitive to the spin-phonon coupling.

ErMnO3 single crystals are studied by polarized first-order and second-order micro-Raman measurements as a function of temperature and compared to previous hexagonal RMnO3 (R =  Y, Ho, Yb) studies. In addition to the resonance effects of the 684 cm−1 mode that are correlated with Mn3+ d–d electronic transitions, some phonon frequencies show anomalous temperature variations suggesting a spin–phonon coupling below TN. The deviation from standard temperature dependence is discussed within a model accounting for the modulation of the exchange interaction by phonon vibrations.

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Separating molecular spin isomers is a challanging task, with potential applications in various fields ranging from astrochemistry to magnetic resonance imaging. A new promissing method for spin-isomer separation is magnetic focusing, a method which was shown to be capable of producing a molecular beam of ortho-water. Here, we present results from a modified magnetic focusing apparatus and show that it can be used to separate the spin isomers of acetylene and methane. From the measured focused profiles of the molecular beams and a numerical simulation analysis we provide estimations for the spin purity and the significantly improved molecular flux obtained with the new setup. Finally, we discuss the spin-relaxation conditions which will be needed to apply this new source for measuring NMR signals of single surface layer.

Infrared active phonons of HoMnO 3 and LuMnO 3 single crystals are studied under an applied magnetic field below Ho 3+ spin ordering at T = 4.2 K. Interestingly, relatively strong mode energy shifts, induced by the magnetic field, are observed in HoMnO 3 but are absent in the nonmagnetic rare-earth compound LuMnO 3 . We associate the large magnetoelectric effects in HoMnO 3 with a mechanism of charge transfer between Ho 3+ and apical oxygen. Also, the exact values of the published polarization change under the applied magnetic field are predicted with no adjustable parameters.

It is known that orthorhombic RMnO3 multiferroics (R = magnetic rare earth) with low symmetry exhibit a large rotating magnetocaloric effect because of their strong magnetocrystalline anisotropy. In this paper, we demonstrate that the hexagonal ErMnO3 single crystals also unveils a giant rotating magnetocaloric effect that can be obtained by spinning them in constant magnetic fields around their a or b axes. When the ErMnO3 crystal is rotated with the magnetic field initially parallel to the c-axis, the resulting entropy change reaches maximum values of 7, 17 and 20 J/kg K under a constant magnetic field of 2, 5 and 7 T, respectively. These values are comparable or even larger than those shown by some of the best orthorhombic phases. More interestingly, the generated anisotropic thermal effect is about three times larger than that exhibited by the hexagonal HoMnO3 single crystal.The enhancement of the rotating magnetocaloric effect in the hexagonal ErMnO3 compound arises from the unique features of Er 3+ magnetic sublattice. In fact, the Er 3+ magnetic moments located at 2a sites experience a first-order metamagnetic transition close to 3 K along the c-axis resulting in a peaked magnetocaloric effect over a narrower temperature range. In contrast, the "paramagnetic" behaviour of Er 3+ magnetic moments within the ab-plane, produces a larger magnetocaloric effect over a wider temperature range. Therefore, the magnetocaloric effect anisotropy is maximized between the c and the ab-directions, leading to a giant rotating magnetocaloric effect. *Mohamed.balli@usherbrooke.ca I. IntroductionBased on the well-known magnetocaloric effect (MCE), magnetic cooling is a trending technology that continues to attract a worldwide interest due to its potential high thermodynamic efficiency as well as its ecofriendly character [1][2][3][4][5][6][7][8]. The implementation of this emergent technology in our daily life would enable to fully suppress the harmful synthetic refrigerants such as fluorinated fluids, usually present in standard refrigerators and air-conditioners [1][2][3][4][5][6][7][8], thus allowing to meet the requirements of several treaties that were universally adopted by the international community aiming to reduce the utilization of CFCs, HCFCs and HFCs gases and, green house gases (GHG) emissions [1]. However, the search for advanced magnetocaloric materials with outstanding thermal, chemical and mechanical properties is necessary for the transfer of magnetic refrigeration technology towards the market place. In this context, a large MCE has been pointed out in a wide variety of magnetocaloric materials including both intermetallics and oxides [1-8]. Some of them such as LaFe13-xSix compounds, Fe2P-type materials and ABO3-based oxides have been successfully tested in room-temperature devices unveiling the bright future of magnetic refrigeration [1]. On the other hand, magnetic materials with excellent caloric effects at the temperature range below 30 K are of great importance in several low-temperature applications...

The mechanism for interconversion between the nuclear spin isomers (NSI) of HO remains shrouded in uncertainties. The temperature dependence displayed by NSI interconversion rates for HO isolated in an argon matrix provides evidence that confinement effects are responsible for the dramatic increase in their kinetics with respect to the gas phase, providing new pathways for o-HO↔p-HO conversion in endohedral compounds. This reveals intramolecular aspects of the interconversion mechanism which may improve methodologies for the separation and storage of NSI en route to applications ranging from magnetic resonance spectroscopy and imaging to interpretations of spin temperatures in the interstellar medium.