Magnetic domain texture and the Dzyaloshinskii-Moriya interaction in Pt/Co/IrMn and Pt/Co/FeMn thin films with perpendicular exchange bias

Abstract

Antiferromagnetic materials present us with rich and exciting physics, which we can exploit to open new avenues in spintronic device applications. We explore perpendicularly magnetized exchange biased systems of Pt/Co/IrMn and Pt/Co/FeMn, where the crossover from paramagnetic to antiferromagnetic behavior in the IrMn and FeMn layers is accessed by varying the thickness. We demonstrate, through magneto-optical imaging, that the magnetic domain morphology of the ferromagnetic Co layer is influenced by the Néel order of the antiferromagnet (AFM) layers. We relate these variations to the anisotropy energy of the AFM layer and the ferromagnet-antiferromagnet (FM-AFM) inter-layer exchange coupling. We also quantify the interfacial Dzyaloshinskii-Moriya interaction (DMI) in these systems by Brillouin light scattering spectroscopy. The DMI remains unchanged, within experimental uncertainty, for different phases of the AFM layers, which allows us to conclude that the DMI is largely insensitive to both AFM spin order and exchange bias. Understanding such fundamental mechanisms is crucial for the development of future devices employing chiral spin textures, such as Néel domain walls and skyrmions, in FM-AFM heterostructures.

Measuring interfacial Dzyaloshinskii-Moriya interaction in ultra-thin magnetic films

“…A strong variation of the D value has been observed and it has been explained taking into account that the main contribution to the DMI come from the interface with the oxide layer. Among the Co articles, Khan et al, 2018 investigates the effect of exchange bias with an antiferromagnetic (AFM) overlayer on Co and confirms that DMI is not influenced by exchange bias or the AFM spin order. Finally, the sinusoidal dependence of the frequency non-reciprocity as a function of the angle between the sample magnetization and the SW wave vector, theoretically predicted by Cortés-Ortuño and Landeros (2013), has been experimentally verified for different multilayer structures (Belmeguenai et al, 2018;Cho et al, 2017;Kim et al, 2016a;Tacchi et al, 2017;Zhang et al, 2015).…”

Antiferromagnetic thickness and temperature dependence of the exchange bias properties of Co/IrMn nanodots and continuous films: A Monte Carlo study

“…The main common behavior is that the exchange field HE and the coercive field HC decrease as the temperature increases at low temperatures. As the temperature increases, HC increases and reaches a peak, while HE still decreases in some studies [10][11][12][13][14] or increases and reaches a peak in other studies [15][16][17]. At higher temperatures, both HE and HC decrease again with increasing temperature.…”

“…It should be noted that most of the theoretical models for EB properties do not account for thermal effects [5][6][7][8][9]. Recently, many experimental studies were conducted to well understand the thermal effects on the EB properties and they have shown some common behaviors of EB properties and some contradictory behaviors [10][11][12][13][14][15][16][17]. The main common behavior is that the exchange field HE and the coercive field HC decrease as the temperature increases at low temperatures.…”

Effect of the Interfacial Dzyaloshinskii–Moriya Interaction on the Spin Waves Eigenmodes of Isolated Stripes and Dots Magnetized In-Plane: A Micromagnetic Study

“…This interaction is an antisymmetric exchange coupling between two nearest spin electrons mediated by an heavy metal under-or overlayer [3][4][5]. For future applications, an accurate measurement of its strength is indispensable, so that different methods have been developed to evaluate it, such as the study of the domain walls motion [6][7][8][9] and the detection of spin waves (SW) by Brillouin light scattering (BLS) [10][11][12][13][14][15][16][17]. Several investigations have been published in the last seven years concerning plain films and multilayers [18,19], while there are only a few investigations concerning patterned nanostructures [20][21][22][23][24][25].…”