Journal Article

Manifestation of magnetic quantum fluctuations in the dielectric properties of a multiferroic

Khim, Seunghyun, Cheong, S.-W., Chun, Sae Hwan, Balicas, L., Harrison, N., Hoon Han, Jung, Jo, Y., Hoon Kim, Kee, Batista, C. D., Kim, Jae Wook, Yi, H. T.

2014

Overview

Insulating magnets can display novel signatures of quantum fluctuations as similar to the case of metallic magnets. However, their weak spin-lattice coupling has made such observations challenging. Here we find that antiferromagnetic (AF) quantum fluctuations manifest in the dielectric properties of multiferroic Ba 2 CoGe 2 O 7 , where a ferroelectric polarization develops concomitant to an AF ordering. Upon application of a magnetic field ( H ), dielectric constant shows a characteristic power-law dependence near absolute zero temperature and close to the critical field H c =37.1 T due to enhanced AF quantum fluctuations. When H > H c , the dielectric constant shows the temperature-dependent anomalies that reflect a crossover from a field-tuned quantum critical to a gapped spin-polarized state. We uncover theoretically that a linear relation between AF susceptibility and dielectric constant stems from the generic magnetoelectric coupling and directly explains the experimental findings, opening a new pathway for studying quantum criticality in condensed matter. Although quantum fluctuations of the spins occur on a local scale, they can have a macroscopic impact on the properties of magnets. Here, the authors observe the macroscopic influence of magnetic quantum fluctuations on the dielectric properties of a multiferroic oxide.

• Publisher: Nature Publishing Group UK,Nature Publishing Group
• Subject: 639/301/119/996 / 639/766/483/1139 / Electrical properties / Fluctuations / Humanities and Social Sciences / Magnetic fields / multidisciplinary / Science / Science (multidisciplinary)