Abstract
Antiferromagnets have traditionally played only a static supporting role in spintronic devices by enhancing the magnetic hardness of a ferromagnetic layer via the interfacial exchange-bias effect. More recently, antiferromagnetic spintronic devices have been demonstrated, including memories in which the antiferromagnetic layer plays an active role in the device [1-6].
Devices based on antiferromagnets can have important advantages over the conventionally ferromagnetic ones. For instance, such advantages can be faster dynamics, no stray fields and insensitivity to external fields.
A key challenge in antiferromagnetic spintronics lays on how to manipulate the compensated moments. It has been demonstrated that relativistic spin torques can provide an efficient way of electrically-manipulating antiferromagnets [5].
Memories based on antiferromagnets have recently been demonstrated, where such spin orbit torques were used to re-orient the moments (writing a given state) and the detection of the moments was done by reading the anisotropic magnetoresistance [6]. In such measurements, the two different states correspond to antiferromagnetic moments perpendicular to each other.
Since the anisotropic magnetoresistance is even in magnetization, it is not straightforward how to distinguish antiferromagnetic moments rotated by 180 degrees. In this work we propose measuring the second harmonics of the anisotropic magnetoresistance [7,8] as a way to distinguish such moments.
We prepared antiferromagnetic memories from CuMnAs. And after electrically orienting the magnetic moments along different directions, we measured the second harmonics resistance.
We also studied the dependence of the second harmonics signal on temperature and probing current.