Evidence of symmetry lowering in antiferromagnetic metal TmB12 with dynamic charge stripes

Precise angle-resolved magnetoresistance (ARMR) and magnetization measurements have revealed (i) strong charge transport and magnetic anisotropy and (ii) emergence of a huge number of magnetic phases in the ground state of isotopicaly 11B-enriched single crystals of TmB12 antiferromagnetic (AF) metal with fcc crystal structure and dynamic charge stripes. We analyze for the first time the angular H-φ phase diagrams of AF state of Tm11B12 reconstructed from experimental ARMR and magnetization data arguing that the symmetry lowering leads to the appearance of several radial phase boundaries between different phases in the AF state. It is proposed that the suppression of the indirect Ruderman–Kittel–Kasuya–Yosida (RKKY) exchange along 〈110〉 directions between nearest neighboring magnetic moments of Tm3+ ions and subsequent redistribution of conduction electrons to quantum fluctuations of the electron density (dynamic stripes) are the main factors responsible for the anisotropy. Essential (more than 25 % at T = 2 K) anisotropy of the Neel field in the (110) plane was found in Tm11B12 unlike to isotropic AF-P boundary in the H-φ phase diagrams of Ho11B12. Magnetoresistance components are discussed in terms of charge carrier scattering on the spin density wave, itinerant ferromagnetic nano-domains and on-site Tm3+ spin fluctuations.

Nonresonant amplification of spin waves through interface magnetoelectric effect and spin-transfer torque

We present a new mechanism for manipulation of the spin-wave amplitude through the use of the dynamic charge-mediated magnetoelectric effect in ultrathin multilayers composed of dielectric thin-film capacitors separated by a ferromagnetic bilayer. Propagating spin waves can be amplified and attenuated with rising and decreasing slopes of the oscillating voltage, respectively, locally applied to the sample. The way the spin accumulation is generated makes the interaction of the spin-transfer torque with the magnetization dynamics mode-selective and restricted to some range of spin-wave frequencies, which is contrary to known types of the spin-transfer torque effects. The interfacial nature of spin-dependent screening allows to reduce the thickness of the fixed magnetization layer to a few nanometers, thus the proposed effect significantly contributes toward realization of the magnonic devices and also miniaturization of the spintronic devices.