Temperature-Dependent Spin Gap in Multiferroic 2D-XY Antiferromagnet Ba2CoGe2O7 Under Applied Magnetic Fields

IEEE Transactions on Magnetics, vol. 59, pp. 1–4

Abstract

We report an inelastic neutron scattering (INS) study on the low-energy magnetic excitations of Ba2CoGe2O7 single crystals under applied magnetic fields for several fixed temperatures. We have observed a sizable spin gap of ≈0.105 meV for the acoustic mode at 2.2 K under zero magnetic fields, whereas no changes in energy of the optical modes at the magnetic zone center are observed under varying temperatures. However, the spin gap of the acoustic mode at finite fields also evolves under varying temperatures and the gap energy decreases with increasing temperature. Interestingly, the difference between the spin gap at 2.2 and 4.6 K is about ≈0.025 meV for all the applied fields of 0.35, 1, and 5 T. Our results enlighten the discussion in detail on understanding the origin of the spin gap in Ba2CoGe2O7.

Authors 9

1. Rajesh Dutta Aachen Institut für Kristallographie

   RWTH Aachen University

   Affiliation as printed

   Institut für Kristallographie, Rheinisch-Westfälische Technische Hochschule (RWTH) Aachen Universität, Aachen, Germany

2. Henrik Thoma Aachen Institut für Kristallographie

   RWTH Aachen University

   Affiliation as printed

   Institut für Kristallographie, Rheinisch-Westfälische Technische Hochschule (RWTH) Aachen Universität, Aachen, Germany

3. B. Roessli

   Paul Scherrer Institute

   Affiliation as printed

   Laboratory for Neutron Scattering and Imaging (LNS), Paul Scherrer Institut (PSI), Villigen, Switzerland

4. Vilmos Kocsis

   RIKEN Center for Emergent Matter Science

   Affiliation as printed

   RIKEN Center for Emergent Matter Science (CEMS), Wako, Saitama, Japan

5. Y. Tokunaga

   RIKEN Center for Emergent Matter Science · The University of Tokyo

   Affiliation as printed

   RIKEN Center for Emergent Matter Science (CEMS), Wako, Saitama, Japan

   Department of Advanced Materials Science, University of Tokyo, Kashiwa, Japan

6. Y. Taguchi

   RIKEN Center for Emergent Matter Science

   Affiliation as printed

   RIKEN Center for Emergent Matter Science (CEMS), Wako, Saitama, Japan

7. Yoshinori Tokura

   RIKEN Center for Emergent Matter Science · The University of Tokyo

   Affiliation as printed

   RIKEN Center for Emergent Matter Science (CEMS), Wako, Saitama, Japan

   Department of Applied Physics, Quantum-Phase Electronics Center, University of Tokyo, Tokyo, Japan

   Department of Applied Physics, University of Tokyo, Hongo, Tokyo, Japan

8. I. Kézsmárki

   University of Augsburg

   Affiliation as printed

   Department of Experimental Physics V, University of Augsburg, Augsburg, Germany

9. Vladimir M. Hutanu Aachen Institut für Kristallographie

   RWTH Aachen University

   Affiliation as printed

   Institut für Kristallographie, Rheinisch-Westfälische Technische Hochschule (RWTH) Aachen Universität, Aachen, Germany