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

Abstract

We report a study of magnetism and magnetic transitions of hexagonal ErMnO3 single crystals by magnetization, specific heat and heat transport measurements. Magnetization data show that the c-axis magnetic field induces three magnetic transitions at 0.8, 12 and 28 T. The specific heat shows a peak at 2.2 K, which is due to a magnetic transition of Er 3+ moments. For low-T thermal conductivity (κ), a clear dip-like feature appears in κ(H) isotherm at 1-1.25 T for H ab; while in the case of H c, a step-like increase is observed at 0.5-0.8 T. The transition fields in κ(H) are in good agreement with those obtained from magnetization, and the anomaly of κ can be understood by a spin-phonon scattering scenario. The natures of magnetic structures and corresponding fieldinduced transitions at low temperatures are discussed.

Magnetoelastic properties of multiferroic hexagonal ErMnO3

“…There are no systematic anomalies in Q -1 from any resonances at these lowest temperatures. Stepwise softening seen below ~3 K for all the resonances in Figure 2c correlates with the small heat capacity anomaly that marks the discrete AFM -FIM1 phase transition at ~2.0-2.5 K in zero field [7,44,45]. The smaller precursor elastic softening below ~6 K also correlates with a dip in the intensity of a magnetic ordering reflection in neutron diffraction patterns shown in Figure 6a of Meier et al [44].…”

“…The paramagnetic structure, PM, is in space group P63cm and the AFM structure orders according to magnetic space group P63'c'm, with a second transition to P63c'm' at low temperature. In zero field these two transitions are marked by distinct anomalies in heat capacity at ~80 and ~2.5 K [7,[45][46][47][48] showed the PM → AFM transition as being driven by ordering of moments at Mn 3+ in directions lying within (001) planes, triggering antiferromagnetic ordering of moments at Er 3+ parallel and antiparallel to [001] on 4b sites (P63'c'm). Er 3+ moments on the 2a sites then order below 10 K, inducing a reorientation of Mn 3+ moments and the Er 3+ moments at 4b sites, to give a structure with magnetic space group P63c'm'.…”

Field-Induced Magnetic Phase Transitions and Rich Phase Diagram of HoMnO3 Single Crystal

“…The absolute value of the magnetization was obtained by a comparison with the data measured by a commercial superconducting quantum interference device (SQUID, Quantum Design). He-3 cryogenic system was employed for the measurements down to~0.7 K. Figure 2b shows the magnetization processes of h-HoMnO 3 at 1.4 K and in a pulsed-field up to 5 T. For H//a, the M increases monotonously with a bend in the vicinity of 3 T. From the derivative dM/dH shown in Figure 2d, we distinguish two magnetic transitions at H c1 = 1 T and H c2 = 2.5 T. The H c1 transition was not detected in the previous work [17], probably due to the relatively slow field-sweeping rate. A hysteresis is seen around H c1 , indicating the nature of a first-order transition.…”

“…Based on the above analysis, the variety of Ho 3+ spin structures in applied fields is proposed in Figure 5. The H c5 transition is characterized by other techniques, such as thermal conductivity [17]. A flip of the Ho 3+ 2a spins at H c6 coincides with a step-like transition at~41 T. The reorientation of spins around H c6 is not continuous, while it will be continuous above this transition in a higher field.…”

Hybridization and Decay of Magnetic Excitations in Two-Dimensional Triangular Lattice Antiferromagnets

“…In this context, one of the key issues is the correlation between spin and lattice degrees of freedom, and thus studying the spinlattice coupling is important for uncovering the underlying microscopic mechanisms in these intriguing multiferroic materials. As such, the experimental evidence of the spin-lattice coupling has been previously observed in a series of experiments: X-ray and neutron diffraction, [133][134][135][136][137] Raman and infrared optical spectroscopy, [138][139][140][141][142][143][144][145][146] thermal conductivity, 147,148 elastic moduli, 77,78 and thermal expansion 7,149 measurements.…”