Z. Y. Zhao

Magnetic phase transitions and magnetoelectric coupling of GdFeO3 single crystals probed by low-temperature heat transport

The low-temperature thermal conductivity (�) of GdFeO3 single crystals is found to be strongly dependent on magnetic field. The low-field �(H) curves show two “dips” for H k a and only one “dip” for H k c, with the characteristic fields having good correspondence with the spin-flop and the spin-polarization transitions. A remarkable phenomenon is that the subKelvin thermal conductivity shows hysteretic behaviors on the history of applying magnetic field, that is, the �(H) isotherms measured with field increasing are larger than those with field decreasing. Intriguingly, the broad region of magnetic field (� 0–3 T) showing the irreversibility of heat transport coincides with that presenting the ferroelectricity. It is discussed that the irreversible �(H) behaviors are due to the phonon scattering by ferroelectric domain walls. This result shows an experimental feature that points to the capability of controlling the ferroelectric domain structures by magnetic field in multiferroic materials.

Ground state and magnetic phase transitions of orthoferriteDyFeO3

Low-temperature thermal conductivity (\kappa), as well as magnetization (M) and electric polarization (P), of multiferroic orthoferrite DyFeO_3 single crystals are studied with H \parallel c. When the crystal is cooled in zero field, M, P, and \kappa all consistently exhibit irreversible magnetic-field dependencies. In particular, with 500 mK < T \le 2 K, all these properties show two transitions at the first run of increasing field but only the higher-field transition is present in the subsequent field sweepings. Moreover, the ultra-low-T (T < 500 mK) \kappa(H) shows a different irreversibility and there is only one transition when the field is swept both up and down. All the results indicate a complex low-T H-T phase diagram involving successive magnetic phase transitions of the Fe^{3+} spins. In particular, the ground state, obtained with cooling to subKelvin temperatures in zero field, is found to be an unexplored phase.

Paramagnetic ground state with field-induced partial order in Nd3Ga5SiO14 probed by low-temperature heat transport

We study the low-temperature heat transport of Nd_3Ga_5SiO_{14}, which is a spin-liquid candidate, to probe the nature of ground state and the effect of magnetic field on the magnetic properties. The thermal conductivity (\kappa) shows a purely phononic transport in zero field. The external magnetic field along the c axis induces a dip-like behavior of \kappa(H), which can be attributed to a simple paramagnetic scattering on phonons. However, the magnetic field along the ab plane induces another step-like decrease of \kappa. This kind of \kappa(H) behavior is discussed to be related to a field-induced partial order, which yields low-energy magnetic excitations that significantly scatter phonons. These results point to a paramagnetic ground state that partial magnetic order can be induced by magnetic field along the ab plane, which is also signified by the low-T specific heat data.

Phonon-glass-like behavior of magnetic origin in single-crystal Tb 2 Ti 2 O 7

Q. J. Li, Z. Y. Zhao, C. Fan, F. B. Zhang, H. D. Zhou, 3 X. Zhao, ∗ and X. F. Sun † Hefei National Laboratory for Physical Sciences at Microscale, University of Science and Technology of China, Hefei, Anhui 230026, People’s Republic of China Department of Physics and Astronomy, University of Tennessee, Knoxville, Tennessee 37996-1200, USA National High Magnetic Field Laboratory, Florida State University, Tallahassee, Florida 32306-4005, USA School of Physical Sciences, University of Science and Technology of China, Hefei, Anhui 230026, People’s Republic of China (Dated: May 30, 2013)

Thermal conductivity of IPA-CuCl3: Evidence for ballistic magnon transport and the limited applicability of the Bose-Einstein condensation model

The heat transport of the spin-gapped material (CH_3)_2CHNH_3CuCl_3 (IPA-CuCl_3), a candidate quantum magnet with Bose-Einstein condensation (BEC), is studied at ultra-low temperatures and in high magnetic fields. Due to the presence of the spin gap, the zero-field thermal conductivity (\kappa) is purely phononic and shows a ballistic behavior at T H_{c1}) and demonstrates limited applicability of the BEC model to IPA-CuCl_3.

Low-temperature heat transport of Nd2CuO4: Roles of Nd magnons and spin-structure transitions

We report the magnetic-field dependence of thermal conductivity (\kappa) of an insulating cuprate Nd_2CuO_4 at very low temperatures down to 0.3 K. It is found that apart from the paramagnetic moments scattering on phonons, the Nd^{3+} magnons can act as either heat carriers or phonon scatterers, which strongly depends on the long-range antiferromagnetic transition and the field-induced transitions of spin structure. In particular, the Nd^{3+} magnons can effectively transport heat in the spin-flopped state of the Nd^{3+} sublattice. However, both the magnon transport and the magnetic scattering are quenched at very high fields. The spin re-orientations under the in-plane field can be conjectured from the detailed field dependence of \kappa.

Low-temperature heat transport in the layered spin-dimer compound Ba 3 Mn 2 O 8

We report a study on the low-temperature heat transport of the Ba

Magnetization, specific heat, and thermal conductivity of hexagonal ErMnO3 single crystals

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Thermal conductivity of the diamond-chain compound Cu3(CO3)2(OH)2

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Low-temperature heat transport in the geometrically frustrated antiferromagnets R2Ti2O7 (R = Gd and Er)

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