Poster Presentation 23rd International Society of Magnetic Resonance Conference 2023

NQR study on spin dimer system TlCuCl3 under hydrostatic pressure (#216)

Takayoshi Yamanaka 1 , Shojiro Kimura 1 , Satoshi Awaji 1 , Hidekazu Tanaka 2
  1. Tohoku University, Sendai, MIYAGI, Japan
  2. Innovator and Inventor Development Platform, Tokyo Institute of Technology, Yokohama, Kanagawa, Japan

A magnetoelectric (ME) effect is a cross-correlation between magnetic and electric properties of matter and has long attracted interest for many multiferroic compounds. This means that the electric dipole moment can be induced by magnetism. For instance, an electric dipole depends on an outer product of two neighboring spins , called vector spin chirality[1]. In this case, the spin-dependent electric dipole is given by a form of two-spin correlation, and therefore, the spontaneous electric polarization can be induced not only in the ordered spin state but also in the quantum spin fluctuated state. There is, however, a lack of studies on the relation between quantum spin fluctuations and ME multiferroics.

Interacting spin dimer system TlCuCl3 is a possible platform for study on the ME effect driven by quantum fluctuations. In this compound, antiferromagnetic (AFM) spin dimers composed of Cu2+ ions are in quantum paramagnetic states down to the lowest temperature[2]. Magnetic fields, however, induce AFM order with a vector spin chirality through Bose-Einstein condensation of triplet magnons. Our group has reported the ferroelectricity in TlCuCl3 under the ordered phase induced by magnetic fields through the dielectric constant measurement and revealed that the electric polarization is proportional to an absolute value of the vector spin chirality[3, 4]. In addition, we found that the first-order magnetic transition at the vicinity of the quantum critical field 5.5 T is shifted to second-order transition, suggesting that the first-order transition is related to the quantum fluctuations.

To investigate the relationship between vector spin chirality and first-order transition, we focus on hydrostatic pressure. A hydrostatic pressure induces the AFM state in TlCuCl3 without vector spin chirality in the absence of magnetic fields.. We try to do nuclear quadrupole resonance measurement, which can observe signals in a zero magnetic field (Fig. 1). 

642f762fbfcc4-AmbPressNQRSP.png

Fig. 1: Nuclear quadrupole resonance spectrum arose from 35, 37Cl nuclear spins in TlCuCl3. We found the signals of two sites (labeled “A” and “B”) among three crystallographic Cl sites.

  1. [1] Y. Tokura et al., Rep. Prog. Phys. 77 076501 (2014). [2] W. Shiramura et al., J. Phys. Soc. Jpn. 66, 1900 (1997). [3] S. Kimura, et al., Nat Commun. 7, 12822 (2016). [4] K. Sakurai, et al., Phys. Rev. B 102, 064104 (2020).