Cascade of field-induced magnetic transitions in a frustrated antiferromagnetic metal

Rapid Communication

Cascade of field-induced magnetic transitions in a frustrated antiferromagnetic metal

A. I. Coldea, L. Seabra, A. McCollam, A. Carrington, L. Malone, A. F. Bangura, D. Vignolles, P. G. van Rhee, R. D. McDonald, T. Sörgel, M. Jansen, N. Shannon, and R. Coldea

Phys. Rev. B 90, 020401(R) – Published 7 July 2014

Abstract

Frustrated magnets can exhibit many novel forms of order when exposed to high magnetic fields. Much less, however, is known about materials where frustration occurs in the presence of itinerant electrons. Here we report thermodynamic and transport measurements on micron-size single crystals of the triangular-lattice metallic antiferromagnet $2 H − {AgNiO}_{2}$ , in magnetic fields of up to 90 T and temperatures down to 0.35 K. We observe a cascade of magnetic phase transitions at 13.5, 20, 28, and 39 T in fields applied along the easy axis, and we combine magnetic torque, specific heat, and transport data to construct the field-temperature phase diagram. The low-field experimental data are compared with theoretical calculations for a frustrated easy-axis Heisenberg model based on realistic parameters for the localized moments of ${AgNiO}_{2}$ . Deviations from this model's predictions are attributed to the role played by the itinerant electrons.

Received 23 December 2013
Revised 17 June 2014

DOI:https://doi.org/10.1103/PhysRevB.90.020401

Authors & Affiliations

A. I. Coldea^1,2,*, L. Seabra^3,4,2, A. McCollam⁵, A. Carrington², L. Malone², A. F. Bangura^6,7,2, D. Vignolles⁸, P. G. van Rhee⁵, R. D. McDonald⁹, T. Sörgel⁶, M. Jansen⁶, N. Shannon^10,1,2, and R. Coldea^1,2

¹Clarendon Laboratory, Department of Physics, University of Oxford, Parks Road, Oxford OX1 3PU, United Kingdom
²H. H. Wills Physics Laboratory, University of Bristol, Tyndall Avenue, Bristol BS8 1TL, United Kingdom
³Department of Physics, Technion – Israel Institute of Technology, Haifa 32000, Israel
⁴Max-Planck-Institut für Physik komplexer Systeme, 01187 Dresden, Germany
⁵High Field Magnet Laboratory, IMM, Radboud University Nijmegen, 6525 ED Nijmegen, The Netherlands
⁶Max-Planck-Institut fur Festkorperforschung, Heisenbergstrasse 1, 70569 Stuttgart, Germany
⁷RIKEN (The Institute of Physical and Chemical Research), Wako, Saitama 351-0198, Japan
⁸Laboratoire National des Champs Magnétiques Intenses (CNRS), 31077 Toulouse, France
⁹National High Magnetic Field Laboratory, Los Alamos National Laboratory, MS E536, Los Alamos, New Mexico 87545, USA
¹⁰Okinawa Institute of Science and Technology, 1919-1 Tancha, Onna-son, Kunigami, Okinawa 904-0495, Japan

^*Corresponding author: amalia.coldea@physics.ox.ac.uk

Article Text (Subscription Required)

Click to Expand

Supplemental Material (Subscription Required)

Click to Expand

References (Subscription Required)

Click to Expand

Issue

Vol. 90, Iss. 2 — 1 July 2014

Reuse & Permissions

Access Options

Author publication services for translation and copyediting assistance advertisement

Images

Figure 1
High magnetic field measurements of micron-size single crystals of $2 H − {AgNiO}_{2}$ . Field dependence of (a) torque and (b) magnetization at constant temperature $T$ for field $H$ nearly along the $c$ axis $(θ \approx 3^{\circ})$ . The inset shows magnetization data for a powder sample at 5 K. (c) Torque data up to 90 T measured at constant temperatures in pulsed magnetic fields on two different samples (top and bottom panels). Magnetic transitions are indicated by arrows and labels. Top inset shows a typical crystal mounted on a piezolever. (d) Field dependence of interlayer transport at constant temperatures below 30 K when $H ∥ c$ (within $θ \approx 3^{\circ})$ . The arrow indicates the deviation from the linear dependence at $H_{c 1}$ . The inset shows the low-temperature resistivity and the arrow indicates the position of the magnetic ordering transition at $T_{N} = 19.5$ K. In all panels, traces at different temperatures are uniformly shifted vertically for clarity.
Reuse & Permissions
Figure 2
(a) The $H - T$ phase diagram of $2 H − {AgNiO}_{2}$ from torque magnetometry (circles), specific heat (triangles), and transport (square). The solid and dashed lines indicate boundaries between different magnetic phases: collinear antiferromagnetic (AFM), field-induced phases I-IV, and paramagnetic (PM). (b) The phase diagram of the classical Heisenberg model on the triangular lattice with first-neighbor $(J_{1} = 1)$ and second-neighbor $(J_{2} = 0.15)$ in-plane interactions, coupling between layers $(J_{⊥} = - 0.15)$ , and easy-axis anisotropy $D = 0.25$ , obtained from Monte Carlo simulation [21]. The axes units are scaled to the point (large solid red circle) where the AFM, canted 1, and plateau phases meet with $T^{*} = 0.3 J_{1}, B^{*} = 1.6 J_{1}$ . In the AFM phase, (c) the spin excitations are gapped, while in the canted 1 phase, (d) electrons can scatter from gapless spin excitations. The solid and dashed lines in the theoretical phase diagram indicate first-order and continuous transitions, respectively.
Reuse & Permissions
Figure 3
Temperature dependence of torque at fixed applied field in (a) experiments and (b) theoretical model. Temperature dependence of specific heat at fixed field in (c) experiment and (d) theory. Identified transitions are indicated by arrows at $T_{c 1}$ , squares at $T_{N}$ , and circles at $T^{'}$ . Calculated (e) torque and (f) magnetization as a function of applied field at constant temperatures compared with experimental data in Figs. 1 and 1 $(θ = 5^{\circ})$ . In the theoretical model, saturation occurs for $H / H^{*} \approx 4.8$ , with $T^{*}$ and $H^{*}$ defined in Fig. 2. Traces at (c),(d) different fields and (e),(f) different temperatures are shifted vertically for clarity.
Reuse & Permissions

Physical Review B

covering condensed matter and materials physics