18 research outputs found
Writing and Reading antiferromagnetic MnAu: N\'eel spin-orbit torques and large anisotropic magnetoresistance
Antiferromagnets are magnetically ordered materials which exhibit no net
moment and thus are insensitive to magnetic fields. Antiferromagnetic
spintronics aims to take advantage of this insensitivity for enhanced
stability, while at the same time active manipulation up to the natural THz
dynamic speeds of antiferromagnets is possible, thus combining exceptional
storage density and ultra-fast switching. However, the active manipulation and
read-out of the N\'eel vector (staggered moment) orientation is challenging.
Recent predictions have opened up a path based on a new spin-orbit torque,
which couples directly to the N\'eel order parameter. This N\'eel spin-orbit
torque was first experimentally demonstrated in a pioneering work using
semimetallic CuMnAs. Here we demonstrate for MnAu, a good conductor with a
high ordering temperature suitable for applications, reliable and reproducible
switching using current pulses and readout by magnetoresistance measurements.
The symmetry of the torques agrees with theoretical predictions and a large
read-out magnetoresistance effect of more than ~ is reproduced by
ab initio transport calculations.Comment: 5 pages, 4 figure
Observation of a new light-induced skyrmion phase in the Mott insulator Cu2OSeO3
We report the discovery of a novel skyrmion phase in the multiferroic
insulator Cu2OSeO3 for magnetic fields below the equilibrium skyrmion pocket.
This phase can be accessed by exciting the sample out of equilibrium with
near-infrared (NIR) femtosecond laser pulses but can not be reached by any
conventional field cooling protocol. From the strong wavelength dependence of
the photocreation process and via spin dynamics simulations, we identify the
magnetoelastic effect as the most likely photocreation mechanism. This effect
results in a transient modification of the magnetic interaction extending the
equilibrium skyrmion pocket to lower magnetic fields. Once created, the
skyrmions rearrange and remain stable over a long time, reaching minutes. The
presented results are relevant for designing high-efficiency non-volatile data
storage based on magnetic skyrmions.Comment: 11 pages, 5 figure
Spectral Measurement of Photon Emission from Individual Gold Nanoparticles Using Scanning Tunneling Microscopy
The light emission spectra of individual Au nanoparticles induced by a scanning tunneling microscope (STM) have been investigated. Two-dimensional ensembles of tunnel-coupled Au particles were prepared by thermal evaporation onto a native oxide silicon wafer in ultrahigh vacuum (10 – 9 mbar). Our STM measurements show a single peak at photon energy 1.6 eV in the tunneling mode and two peaks at 2.2 eV (connected with the Mie plasmon) and 1.45 eV (a new peak which was not discussed in literature before) in the field emission mode
Experimental determination of exchange constants in antiferromagnetic Mn2Au
Mn2Au is an important antiferromagnetic (AF) material for spintronics applications. Due to its very high Neel temperature of about 1500 K, some of the basic properties are difficult to explore, such as the AF susceptibility and the exchange constants. Experimental determination of these parameters is further hampered in thin films by the unavoidable presence of uncompensated and quasiloose spins on antisites and at interfaces. Using x-ray magnetic circular dichroism (XMCD), we measured induced perpendicular spin and orbital moments for a Mn2Au(001) film in fields up to +/- 8 T. By performing these measurements at a low temperature of 7 K and at room temperature (RT), we were able to separate the loose spin contribution from the susceptibility of AF coupled spins. The value of the AF exchange constant obtained with this method for a 10-nm-thick Mn2Au(001) film is (22 +/- 5) meV
Solvent-induced high-spin transition in double-decker 3d–4f metallacrowns
Element-specific magnetic spin and orbital magnetic moments of 3d-4f double-decker metallacrown molecules have been investigated using x-ray magnetic circular dichroism. The double-decker metallacrowns comprise one rare-earth Gd(III) or Tb(III) ion embedded between two squared scaffolds of four Ni(II) ions. We observe a strong increase of the Ni(II) moments if the molecules are dissolved in methanol, indicating a spin crossover from a low-spin to a high-spin state. In contrast, dichloromethane does not change the spin state. This result is explained by a change of the coordination environment of nickel. The comparison of charge-transfer multiplet calculations with the experimental absorption spectra confirm the different ligand fields