Antiferromagnetic (AF) spintronics received an enormous impulse after the first demonstrations of electrical switching of the AF order [1]. However, a lot of these observations can equally well be explained by non-magnetic, parasitic effects caused by the same electrical current pulses that are intended to manipulate the magnetic state of the AF [2]. While it is possible to distinguish between magnetic and non-magnetic effects using imaging techniques that can resolve the AF order [3], these techniques are usually very complex. Moreover, since they require access to the AF layer, they are not suitable for systems where the AF is buried beneath other layers. Our approach is to distinguish between the magnetic and non-magnetic effects by suppressing the magnetic effects using high magnetic fields. In this contribution, we study the high magnetic field behavior of the electrical switching of thin-film AFs NiO and CoO, using the devices shown in Fig. 1. We perform switching experiments in magnetic fields up to 16 Tesla (Fig. 2). The measurements show that these high magnetic fields indeed suppress the current-induced switching of the AF order, whereas the thermal effects remain unaffected. Hence, this technique allows to irrefutably separate the magnetic and non-magnetic effects. These results are corroborated by a model accounting for the multi-domain character of the AF. Finally, the experiments with CoO yield an unexpected dependence of the magnetic configuration on the direction of the high magnetic fields. This indicates an unexpectedly complex magnetic anisotropy in CoO that depends on the magnetic field strength and orientation, most likely due to unquenched orbital momentum. These results both demonstrate that combining electrical methods with strong magnetic fields can be a valuable tool for AF spintronics, and give invaluable insight into the interplay of spin-Hall magnetoresistance and thermal effects as well as the domain structure and complex anisotropy of thin-film antiferromagnets.

![](https://assets.underline.io/uploads/markdown_image/1/image/1fb212d0af0688a1f81826c7b8bf2f9a.jpg)

Fig. 1: Micrograph of the device used for the experiments.

![](https://assets.underline.io/uploads/markdown_image/1/image/e89ac11416c899724e28149f7ee39cf4.jpg)

Fig. 2: Switching amplitude as a function of magnetic field. The lines are calculated with the model; the pie charts represent the modeled domain distribution.

Suppressing Electrical Switching of Antiferromagnets with High Magnetic Fields

Antiferromagnets (AF) have many potential applications in spintronics such as data storage or long-range spin transport devices. The control of spins in AF by electrical current is proven to be possible by different mechanisms [1,2] but it remains challenging to verify experimentally [3]. Such detection can be unambiguously performed with the use of magnetic imaging techniques [4]. However, they are typically sensitive to the topmost layer and cannot be applied in more complex structures where the AF is buried far from the top interface. To mitigate this problem, we present a study of electrical signals in switching experiment in various temperatures for CoO. Basing on this temperature dependence of electrical data for AF CoO thin film we extract patterns that do not follow the trend expected for thermal effects but are probably fingerprints of magnetic changes. In characterization experiments for CoO, magnetoresistance studies for CoO reveal clear spin-flop transitions and pronounced antiferromagnetic hysteresis loops due to strong in-plane anisotropy. Magnetoresistance shows abrupt changes in Rxy around 7 T (240K) when the magnetic field is aligned along [110] axes (easy axes). They can be attributed to spin-flop transitions observed by means of Spin Hall Magnetoresistance. This behavior is hysteretic and absent when the field is aligned along [100] directions (hard axes) or in T = 304 K (above Néel temperature TN). It confirms the presence of biaxial anisotropy in CoO and easy axes along [110] in agreement with literature [5]. Hysteresis loops in Rxy when the magnetic field is rotated with respect to crystalline axes are observed up to the highest tested magnetic fields due to the strong in-plane anisotropy. In the actual switching experiments of CoO (Fig. 1), the temperature dependence of the transverse resistance Rxy variations after current pulses applied in alternating directions in a CoO | Pt device is examined. Resistivity variations due to thermal effects (such as asymmetric heating) increase with increasing temperature or current pulse amplitude and persist above TN of CoO. However, at lower current magnitudes we find a pattern that decreases with increasing temperature and vanishes above TN suggesting its magnetic origin (Fig. 2). In conclusion, we demonstrate that manipulation of temperature may help to gain more insight into the nature of electrical signals variations in experiments with antiferromagnets. These presented experimental findings can be important for current research acitivities towards using antiferromagnets in real spintronic devices.

**References:**

[1] P. Wadley, B. Howells, J. Zelezny et al., Science, 351, 587 (2016). [2] L. Baldrati, O. Gomonay, A. Ross et al., Phys. Rev. Lett., 123, 177201 (2019). [3] C. C. Chiang, S. Y. Huang, D. Qu, et al., Phys. Rev. Lett., 123, 227203 (2019). [4] M. J. Grzybowski, P. Wadley, K. W. Edmonds et al., Phys. Rev. Lett., 118, 057701 (2017). [5] L. Baldrati, C. Schmitt, O. Gomonay et al., Phys. Rev. Lett., 125, 077201 (2020).

**Images:**

![](https://assets.underline.io/uploads/markdown_image/1/image/dc1c0c50382cc7fa878e0b12ff757dcd.jpg)
Fig. 1 The switching experiment for CoO (5 nm) | Pt (5 nm) thin films device where the transverse resisitivity Rxy is measured after each pulse of high current (the direction of the pulsing current is changed to perpendicular one after each 5 pulses). Interestingly, above TN the pattern visible in 240K is not present.

![](https://assets.underline.io/uploads/markdown_image/1/image/151b408e9acc0384e83f5b04392a240d.jpg)
Fig. 2 The magnitude of Rxy variations after pulsing in orthogonal directions in CoO for 24 mA current diminishes with increasing temperature and is practically invisible in room temperature (above TN). This trend is different for higher currents where Rxy variations increases with T as expected for thermal effects.

 Switching experiment of antiferromagnetic CoO in different temperatures

**Session chairs:** Jean Anne Incorvia, University of Texas at Austin and Vincent Baltz, Spintec



GOO - Antiferromagnetic Spintronics I

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FG: Antiferromagnetic Spintronics I

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Suppressing Electrical Switching of Antiferromagnets with High Magnetic Fields

Switching experiment of antiferromagnetic CoO in different temperatures