Magnetic Frustration, Phase Competition, and the Magnetoelectric Effect inNdFe3(BO3)4

Abstract

We present an element selective resonant magnetic x-ray scattering study of NdFe3(BO3)4 as a function of temperature and applied magnetic field. Our measurements show that the magnetic order of the Nd sublattice is induced by the Fe spin order. When a magnetic field is applied parallel to the hexagonal basal plane, the helicoidal spin order is suppressed and a collinear ordering, where the moments are forced to align in a direction perpendicular to the applied magnetic field, is stabilized. This result excludes a noncollinear spin order as the origin of the magnetically induced electric polarization in this compound. Instead our data imply that magnetic frustration results in a phase competition, which is the origin of the magnetoelectric response.

Tracking the continuous spin-flop transition inNi3TeO6by infrared spectroscopy

“…1 Considering the foundational role of Heisenberg exchange striction in generating spin-lattice coupling, the complex magnetism, and the enormous field-induced polarization changes, direct measurements of the elementary excitations are important for understanding Ni 3 TeO 6 and other members of this promising family of compounds. [9][10][11][12][13][14][15] Here, we employ infrared vibrational spectroscopy to reveal for the first time the lattice dy- namics of Ni 3 TeO 6 over a broad range of temperature and magnetic field. Our measurements uncover frequency shifts in the phonons across T N and through the fielddriven spin-flop transition, demonstrating that the lattice is sensitive to changes in the microscopic spin arrangement.…”

Control of coexisting magnetic phases by electric fields inNdFe3(BO3)4

“…This strong magnetoelectric coupling sparked significant interest in NdFe 3 (BO 3 ) 4 and immediately raised the question about its microscopic origin. Recent x-ray diffraction experiments already provided microscopic insight and implied that the finite P a is related to the magnetic field-induced CM order [17,18]. In principle, the strong magnetoelectric coupling discovered in previous studies should also enable to alter the magnetic order of NdFe 3 (BO 3 ) 4 by applying external electric fields.…”

“…1, where, for the sake of simplicity, only the two magnetic sublattices of Fe and Nd are shown. These two sublattices are magnetically coupled and undergo two magnetic phase transitions as a function of temperature [15][16][17]: upon cooling, commensurate magnetic (CM) order sets in first at T N ≈ 30 K. In this phase the spins are ordered in a collinear fashion, forming ferromagnetic (FM) ab-planes, which are coupled antiferromagnetically (AFM) along the c-direction. The magnetic The material can be described using the rhombohedral space group R32 with hexagonal unit cell parameters a ≈ 9.5Å and c ≈ 7.5Å at room temperature [14].…”

“…By applying a voltage across the two electrodes, electric fields up to E =8.8 · 10 4 V/m parallel to the crystallographic a axis were generated. We set the photon energy to the Nd L 2 edge at 6.726 keV in order to probe directly the magnetic order of the Nd-sublattice, which, in turn, also reflects the magnetic order of the Fe-sublattice [17]. For the L-scans shown in the following, the incoming light was horizontally (π) polarized and no polarization analyzer was used.…”

Nuclear Resonant Surface Diffraction of Synchrotron Radiation

“…While the width of the Bragg peaks is coupled to the crystal quality or strain of magnetic lattices, their peak position and intensity yield lattice parameters, content of the unit cell, or the arrangement of magnetic moments. Monitoring these diffraction peaks under the influence of external fields, pressure, temperature variation, or growth thus enables a detailed in situ characterization of nanomagnetic systems.During the last few decades, resonant x-ray diffraction and reflectometry were extensively applied to reveal the magnetic structure of various crystalline alloys [4][5][6] and superlattices [7][8][9][10][11][12]. Despite the growing need for the characterization of extended patterned magnetic structures like spin ice [13,14] or Skyrmion thin film systems [15][16][17], only a few resonant magnetic x-ray diffraction studies on such systems were carried out [18][19][20][21].…”