ABSTRACT
In this work we examine synthetic antiferromagnetic structures consisting of two, three, and four antiferromagnetic coupled layers, i.e. bilayers, trilayers, and tetralayers. We vary the thickness of the ferromagnetic layers across all structures and, using a macrospin formalism, find that the nearest neighbor exchange interaction between layers is consistent across all structures for a given thickness of the ferromagnetic layer. Our model and experimental results demonstrate significant differences in how the static equilibrium states of even and odd-layered structures evolve as a function of the external field. Even layered structures continuously evolve from a collinear antiferromagnetic state to a spin canted non-collinear magnetic configuration that is mirror-symmetric about the external field. In contrast, odd-layered structures begin with a ferrimagnetic ground state; at a critical field, the ferrimagnetic ground state evolves into a non-collinear state with broken symmetry. Specifically, the magnetic moments found in the odd-layered samples possess stable static equilibrium states that are no longer mirror-symmetric about the external field after a critical field is reached.
ABSTRACT
When time-reversal symmetry is broken, the low-energy description of acoustic lattice dynamics allows for a dissipationless component of the viscosity tensor, the phonon Hall viscosity, which captures how phonon chirality grows with the wave vector. In this work, we show that, in ionic crystals, a phonon Hall viscosity contribution is produced by the Lorentz forces on moving ions. We calculate typical values of the Lorentz force contribution to the Hall viscosity using a simple square lattice toy model, and we compare it with literature estimates of the strengths of other Hall-viscosity mechanisms.
ABSTRACT
This corrects the article DOI: 10.1103/PhysRevLett.121.187204.
ABSTRACT
Prototypes of quantum impurities, such as NV and SiV color centers in diamond, have garnered much attention due to their minimally invasive and high-resolution magnetic field and thermal sensing. Here, we investigate quantum-impurity relaxometry as a method for probing collective excitations in magnetic insulators. We develop a general framework to relate the measurable quantum-impurity relaxation rates to the intrinsic dynamic properties of a magnetic system via the noise emitted by the latter. We suggest, in particular, that the quantum-impurity relaxometry is sensitive to dynamic phase transitions, such as magnon condensation, and can be deployed to detect signatures of the associated coherent spin dynamics, both in ferromagnetic and antiferromagnetic systems. Finally, we discuss prospects to nonintrusively probe spin-transport regimes and measure the associated transport coefficients in magnetic insulators.
ABSTRACT
We investigate coupled spin and heat transport in easy-plane magnetic insulators. These materials display a continuous phase transition between normal and condensate states that is controlled by an external magnetic field. Using hydrodynamic equations supplemented by Gross-Pitaevski phenomenology and magnetoelectric circuit theory, we derive a two-fluid model to describe the dynamics of thermal and condensed magnons, and the appropriate boundary conditions in a hybrid normal-metal-magnetic-insulator-normal-metal heterostructure. We discuss how the emergent spin superfluidity can be experimentally probed via a spin Seebeck effect measurement.
