Kumar C M N, Xiao Y, Nair H S, Voigt J, Schmitz B, Chatterji T, Jalarvo N H, Brückel Th
Jülich Centre for Neutron Science JCNS and Peter Grünberg Institut PGI, JARA-FIT, Forschungszentrum Jülich, 52425 Jülich, Germany. Jülich Centre for Neutron Science JCNS, Forschungszentrum Jülich GmbH, Outstation at SNS, Oak Ridge National Laboratory, Oak Ridge, TN 37831, USA. Chemical and Engineering Materials Division, Spallation Neutron Source, Oak Ridge National Laboratory, Oak Ridge, TN 37831, USA.
J Phys Condens Matter. 2016 Nov 30;28(47):476001. doi: 10.1088/0953-8984/28/47/476001. Epub 2016 Sep 16.
We report a comprehensive specific heat and inelastic neutron scattering study to explore the possible origin of multiferroicity in HoCrO3. We have performed specific heat measurements in the temperature range 100 mK-290 K and inelastic neutron scattering measurements were performed in the temperature range 1.5-200 K. From the specific heat data we determined hyperfine splitting at 22.5(2) μeV and crystal field transitions at 1.379(5) meV, 10.37(4) meV, 15.49(9) meV and 23.44(9) meV, indicating the existence of strong hyperfine and crystal field interactions in HoCrO3. Further, an effective hyperfine field is determined to be 600(3) T. The quasielastic scattering observed in the inelastic scattering data and a large linear term [Formula: see text] mJ mol(-1) K(-2) in the specific heat is attributed to the presence of short range exchange interactions, which is understood to be contributing to the observed ferroelectricity. Further the nuclear and magnetic entropies were computed to be, ∼17.2 Jmol(-1) K(-1) and ∼34 Jmol(-1) K(-1), respectively. The entropy values are in excellent agreement with the limiting theoretical values. An anomaly is observed in the peak position of the temperature dependent crystal field spectra around 60 K, at the same temperature an anomaly in the pyroelectric current is reported. From this we could elucidate a direct correlation between the crystal electric field excitations of Ho(3+) and ferroelectricity in HoCrO3. Our present study, along with recent reports, confirm that HoCrO3, and RCrO3 (R = rare earth) in general, possess more than one driving force for the ferroelectricity and multiferroicity.
我们报告了一项关于综合比热和非弹性中子散射的研究，以探究 HoCrO₃ 中多铁性的可能起源。我们在 100 mK - 290 K 的温度范围内进行了比热测量，并在 1.5 - 200 K 的温度范围内进行了非弹性中子散射测量。从比热数据中，我们确定了 22.5(2) μeV 的超精细分裂以及 1.379(5) meV、10.37(4) meV、15.49(9) meV 和 23.44(9) meV 的晶体场跃迁，这表明 HoCrO₃ 中存在强超精细和晶体场相互作用。此外，确定有效超精细场为 600(3) T。在非弹性散射数据中观察到的准弹性散射以及比热中较大的线性项 [公式：见文本] mJ mol⁻¹ K⁻² 归因于短程交换相互作用的存在，据信这有助于观察到的铁电性。此外，计算出核熵和磁熵分别约为 17.2 Jmol⁻¹ K⁻¹ 和 34 Jmol⁻¹ K⁻¹。这些熵值与极限理论值非常吻合。在约 60 K 处，观察到与温度相关的晶体场光谱的峰值位置出现异常，在相同温度下，报道了热释电电流出现异常。由此我们可以阐明 Ho³⁺ 的晶体电场激发与 HoCrO₃ 中铁电性之间的直接关联。我们目前的研究以及近期的报告证实，一般而言，HoCrO₃ 和 RCrO₃（R = 稀土）具有不止一种铁电性和多铁性的驱动力。
