Antiferromagnets provide greater stability than their ferromagnetic counterparts, but antiferromagnetic spin textures and nanostructures also exhibit more complex, and often faster, dynamics, ...offering new functionalities for spintronics devices.
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.
Antiferromagnetic spintronics Baltz, V.; Manchon, A.; Tsoi, M. ...
Reviews of modern physics,
02/2018, Letnik:
90, Številka:
1
Journal Article
Recenzirano
Odprti dostop
Antiferromagnetic materials could represent the future of spintronic applications thanks to the numerous interesting features they combine: they are robust against perturbation due to magnetic ...fields, produce no stray fields, display ultrafast dynamics, and are capable of generating large magnetotransport effects. Intense research efforts over the past decade have been invested in unraveling spin transport properties in antiferromagnetic materials. Whether spin transport can be used to drive the antiferromagnetic order and how subsequent variations can be detected are some of the thrilling challenges currently being addressed. Antiferromagnetic spintronics started out with studies on spin transfer and has undergone a definite revival in the last few years with the publication of pioneering articles on the use of spin-orbit interactions in antiferromagnets. This paradigm shift offers possibilities for radically new concepts for spin manipulation in electronics. Central to these endeavors are the need for predictive models, relevant disruptive materials, and new experimental designs. This paper reviews the most prominent spintronic effects described based on theoretical and experimental analysis of antiferromagnetic materials. It also details some of the remaining bottlenecks and suggests possible avenues for future research. This review covers both spin-transfer-related effects, such as spin-transfer torque, spin penetration length, domain-wall motion, and “magnetization” dynamics, and spin-orbit related phenomena, such as (tunnel) anisotropic magnetoresistance, spin Hall, and inverse spin galvanic effects. Effects related to spin caloritronics, such as the spin Seebeck effect, are linked to the transport of magnons in antiferromagnets. The propagation of spin waves and spin superfluids in antiferromagnets is also covered.
We investigate the current-induced switching of the Néel order in NiO(001)/Pt heterostructures, which is manifested electrically via the spin Hall magnetoresistance. Significant reversible changes in ...the longitudinal and transverse resistances are found at room temperature for a current threshold lying in the range of 10^{7} A/cm^{2}. The order-parameter switching is ascribed to the antiferromagnetic dynamics triggered by the (current-induced) antidamping torque, which orients the Néel order towards the direction of the writing current. This is in stark contrast to the case of antiferromagnets such as Mn_{2}Au and CuMnAs, where fieldlike torques induced by the Edelstein effect drive the Néel switching, therefore resulting in an orthogonal alignment between the Néel order and the writing current. Our findings can be readily generalized to other biaxial antiferromagnets, providing broad opportunities for all-electrical writing and readout in antiferromagnetic spintronics.
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.
Spin caloritronic nano-oscillator Safranski, C; Barsukov, I; Lee, H K ...
Nature communications,
07/2017, Letnik:
8, Številka:
1
Journal Article
Recenzirano
Odprti dostop
Energy loss due to ohmic heating is a major bottleneck limiting down-scaling and speed of nano-electronic devices, and harvesting ohmic heat for signal processing is a major challenge in modern ...electronics. Here, we demonstrate that thermal gradients arising from ohmic heating can be utilized for excitation of coherent auto-oscillations of magnetization and for generation of tunable microwave signals. The heat-driven dynamics is observed in Y
Fe
O
/Pt bilayer nanowires where ohmic heating of the Pt layer results in injection of pure spin current into the Y
Fe
O
layer. This leads to excitation of auto-oscillations of the Y
Fe
O
magnetization and generation of coherent microwave radiation. Our work paves the way towards spin caloritronic devices for microwave and magnonic applications.Harvesting ohmic heat for signal processing is one of major challenges in modern electronics and spin caloritronics, but not yet well accomplished. Here the authors demonstrate a spin torque oscillator device driven by pure spin current arising from thermal gradient across an Y
Fe
O
/Pt interface.
Abstract
Thermoelectric effects have been applied to power generators and temperature sensors that convert waste heat into electricity. The effects, however, have been limited to electrons to occur, ...and inevitably disappear at low temperatures due to electronic entropy quenching. Here, we report thermoelectric generation caused by nuclear spins in a solid: nuclear-spin Seebeck effect. The sample is a magnetically ordered material MnCO
3
having a large nuclear spin (
I
= 5/2) of
55
Mn nuclei and strong hyperfine coupling, with a Pt contact. In the system, we observe low-temperature thermoelectric signals down to 100 mK due to nuclear-spin excitation. Our theoretical calculation in which interfacial Korringa process is taken into consideration quantitatively reproduces the results. The nuclear thermoelectric effect demonstrated here offers a way for exploring thermoelectric science and technologies at ultralow temperatures.
The scalability of quantum networks based on solid-state spin qubits is hampered by the short range of natural spin-spin interactions. Here, we propose a scheme to entangle distant spin qubits via ...the soft modes of an antiferromagnetic domain wall (DW). As spin qubits, we focus on quantum impurities (QIs) placed in the vicinity of an insulating antiferromagnetic thin film. The low-energy modes harbored by the DW are embedded in the antiferromagnetic bulk, whose intrinsic spin-wave dynamics have a gap that can exceed the THz range. By setting the QI frequency and the temperature well within the bulk gap, we focus on the dipolar interaction between the QI and two soft modes localized at the DW. One is a stringlike mode associated with transverse displacements of the DW position, while the dynamics of the other, corresponding to planar rotations of the Néel order parameter, constitute a spin superfluid. By choosing the geometry in which the QI does not couple to the string mode, we use an external magnetic field to control the gap of the spin superfluid and the qubit-qubit coupling it engenders. We suggest that a tunable micron-range coherent coupling between qubits can be established using common antiferromagnetic materials.
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