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The symmetry, microscopy and spectroscopy signatures of altermagnetism are reviewed, and compared with traditional ferromagnetism and Néel antiferromagnetism, and magnetic phases with symmetry-protected compensated non-collinear spin orders.

Antiferromagnets offer the potential for higher speed and density than ferromagnetic materials for spintronic devices. Here, Reimers et al study the domain structure of CuMnAs, demonstrating the role of defects in stabilizing the location and orientation of antiferromagnetic domain walls.

A technique that allows the electrical detection of spin-polarized transport in semiconductors without disturbing the spin-polarized current or using magnetic elements has now been demonstrated. The approach could lead to the integration of spintronics elements into semiconductor microelectronic circuits.

Non-local transport measurements on mercury telluride quantum wells show clear signatures of the ballistic spin Hall effect. The ballistic nature of the experiment allows the observed effect to be interpreted as a direct consequence of the band structure of these semiconductor nanostructures, rather that being caused by impurity scattering.

The zero net moment of antiferromagnets makes them insensitive to magnetic fields and enables ultrafast dynamics promising for novel spintronics. Here the authors achieved pulse current induced Néel vector switching in Mn₂Au(001) epitaxial thin films, which is associated with a large magnetoresistive effect allowing simple read-out.

Spin transfer torque—the transfer of angular momentum from a spin-polarized current to a ferromagnet’s magnetization—has already found commercial application in memory devices, but the underlying physics is still not fully understood. Researchers now demonstrate the crucial role played by the polarization of the laser light that generates the current; a subtle effect only evident when isolated from other influences such as heating.

Experimental observations and theoretical analysis provide evidence that the spin polarization of the spin-spiral type II multiferroic NiI₂ exhibits p-wave magnetism and its spin chirality is related to ferroelectric polarization, which can be electrically controlled. 

Using photoemission spectroscopy and ab initio calculations, evidence is given of two distinct unconventional mechanisms of lifted Kramers spin degeneracy generated by the altermagnetic phase of centrosymmetric MnTe with vanishing net magnetization.

Antiferromagnets are promising candidates to build terahertz spintronic devices. However, manipulating and detecting their terahertz spin dynamics remains key challenges. Here, Rongione et al. demonstrate both broadband and narrowband terahertz emission from an antiferromagnet/heavy metal heterostructure using spin-phonon interactions.

A novel non-thermal photomagnetic torque originating from spin–orbit coupling of non-equilibrium photocarriers excited by helicity-independent laser pulses is found in (Ga,Mn)As thin films. It differs fundamentally from optical spin–transfer torque. The possibility of studying spin–orbit torques on short timescales achievable by pump–probe magneto-optical measurements is demonstrated.

Antiferromagnets offer faster operation speed and immunity to stray fields, however, readout of the Neel vector is difficult. Here, Bommanaboyena et al present a heterostructure of a ferromagnet and antiferromagnet, combining easy readout with the benefits of antiferromagnetic spintronics.

The spin Hall effect plays a central role in generating and manipulating spin currents, but its magnitude is ultimately fixed by spin–orbit coupling effects. It is now shown that the spin-Hall-effect angle can be tuned electrically in GaAs.

Antiferromagnets have attracted interest for spin-based information processing due to their resilience to stray magnetic fields and extremely rapid spin dynamics, however, long range spin wave transport has only been shown in one type of antiferromagnet thus far. Here, Das et al demonstrate long range spin wave transport in antiferromagnetic YFeO3.

The detection of spin–orbit torques in a non-centrosymmetric magnetic Heusler alloy at room temperature could guide the search for materials whose magnetism can efficiently be manipulated using electrical currents.

A type of spin–orbit torque originating from the Berry curvature is identified in ferromagnets with bulk inversion asymmetry.

Hitherto, only circularly polarized antiferromagnetic (AFM) spin-waves (SWs) were expected to convey spin-information. Here, the authors present persistent spin-transport over long distances in the easy-plane AFM phase of hematite, α-Fe₂O₃, via linearly polarized SW pairs with ultra-low damping.

Measurements with a lateral spin pumping device architecture suggest that long spin diffusion lengths of more than 1 μm are possible in conjugated polymer systems that have a sufficiently high spin density.

The transport and relaxation mechanisms in organic semiconductors are still insufficiently understood, but measurements now show that in these materials polarons carry pure spin currents over extended distances with long relaxation times, and uncover the role of spin-orbit coupling in this process.

New developments in spintronics based on antiferromagnetic materials show promise for improved fundamental understanding and applications in technology.

Antiferromagnets are expected to be a key part of next generation electronic devices however their magnetic interactions prove difficult to access. Here, the authors demonstrate that the surface sensitive spin-Hall magnetoresistance, along with a simple analytical model, can successfully probe the internal anisotropies of the model antiferromagnet hematite (α-Fe₂O₃).