High-field recovery of the undistorted triangular lattice in the frustrated metamagnetCuFeO2

Abstract

Link to publication in University of Groningen/UMCG research database Citation for published version (APA): Lummen, T. T. A., Strohm, C., Rakoto, H., Nugroho, A. A., & van Loosdrecht, P. H. M. (2009 Pulsed-field magnetization experiments extend the typical metamagnetic staircase of CuFeO 2 up to 58 T to reveal an additional first-order phase transition at high field for both the parallel and perpendicular field configuration. Virtually complete isotropic behavior is retrieved only above this transition, indicating the high-field recovery of the undistorted triangular lattice. A consistent phenomenological rationalization for the field dependence and metamagnetism crossover of the system is provided, demonstrating the importance of both spin-phonon coupling and a small field-dependent easy-axis anisotropy in accurately describing the magnetization process of CuFeO 2 . Metamagnetism typically refers to any material that, upon variation in the externally applied magnetic field, exhibits an abrupt change in magnetization. In general, the phase diagrams of materials undergoing field-induced magnetic transitions can be rationalized according to the degree of magnetic anisotropy in the materials.1 In highly anisotropic systems, spins are effectively restricted to align ͑anti͒parallel to the magnetic easy-axis and magnetic transitions typically involve discontinuous spin reversals, leading to first-ordertype metamagnetic transitions. As for isotropic ͑weakly anisotropic͒ systems this directional restriction is relieved ͑strongly reduced͒, transitions in such materials often reflect the onset of a continuous, second-order-type reorientation of the local spins. Another source of exotic magnetic transitions is geometrical magnetic frustration, which occurs when a specific lattice geometry prevents the simultaneous minimization of all magnetic exchange interactions, thus introducing a high spin degeneracy.2 The simultaneous occurrence of both these phenomena and the interplay between them leads to intricate, diverse, and rich physics, yielding many captivating magnetic phases ranging from spin liquids and ices to multiferroic spiral phases. [3][4][5][6] Here the focus is on the delafossite semiconductor CuFeO 2 , an arche-type triangular lattice antiferromagnet, in which the Fe 3+ ions stack in hexagonal layers along the c axis ͓Fig. 1͑a͔͒. In spite of the expected Heisenberg nature of the Fe 3+ spins ͑3d 5 , S =5/ 2, and L =0͒, CuFeO 2 does not order in the noncollinear 120°spin configuration at low temperature. Instead, after undergoing successive phase transitions at T N1 Ϸ 14 K and T N2 Ϸ 11 K, lowering the symmetry from hexagonal ͑R3m͒ to monoclinic, 7-9 the system adopts a collinear, two-up two-down order, with moments aligned ͑anti͒parallel along the c axis ͓Fig. 1͑b͔͒ ͑Ref. 10͒. The collinear ground state is supposedly stabilized through the strong spin-lattice coupling in CuFeO 2 , 7-9,11 which induces a structural distortion through the "spin Jahn-Teller" effect. 12,13 Alternatively, this scalene triangle distorti...

Anisotropic magnetic field responses of ferroelectric polarization in the trigonal multiferroicCuFe1−xAlxO2Nakajima1, Mitsuda2, Kanetsuki3 et al. 2010Phys. Rev. B10270View full textAdd to dashboardCite

“…9(d) and 9(e), we show the H c -dependence of the magnetization and P up to 55 T, respectively. Although, in this paper, we do not focus on the highmagnetic-field behavior in this system, it is worth mentioning here that the fifth-magnetic-field-induced phase transition, which has been recently found in pure CFO, 31,32 was also observed in CFAO(x = 0.015) around H = 48 T. No finite electric polarization was detected in the magnetic-field-induced phases including the 'fifth' phase.…”

Anisotropic lattice dynamics and intermediate-phase magnetism in delafossiteCuFeO2

“…The stabilization of the Ising-like 4SL structure can be attributed to a low-temperature structural distortion resulting in unequal nearest-neighbor exchange interactions [13,14,18,19]. Alternatively, the distortion may yield a weak magnetic anisotropy [20], which in combination with a rather strong spin-phonon coupling can give rise to the Isinglike behavior [2,3,21]. The relevance of the coupling between vibrational properties and magnetic degrees of freedom for both zero field phase transitions in CuFeO 2 was also pointed out in Refs.…”

“…The magnetic phase diagram of CuFeO 2 proves to be particularly rich with various magnetic phases at low temperatures, high magnetic fields [1][2][3][4], and high pressures [5,6]. Ferroelectricity [7] in CuFeO 2 and its connection to the magnetic order is the subject of ongoing studies [8,9].…”

Spin-wave dynamics for the high-magnetic-field phases of the frustrated CuFeO2antiferromagnet: Predictions for inelastic neutron scattering

“…At 34 T, the 3-SL phase smoothly transforms into a conical-type phase. A different conical phase appears at about 50 T [18][19][20] . Finally, all spins become aligned and the CL-1 (ferromagnetic) phase is reached at 70 T 22 .…”

“…The black line in Fig. 1(a) denotes the predicted trajectory for CuFeO 2 with increasing magnetic field, where anisotropy is assumed to decrease with magnetic field, as indicated experimentally 18,19 .…”