Hysteretic Behavior of Angular Dependence of Exchange Bias inFeNi/FeMnBilayers

Abstract

For FeNi/FeMn bilayers, the angular dependence of exchange bias shows hysteresis between clockwise and counterclockwise rotations, as a new signature. The hysteresis decreases for thick antiferromagnet layers. Calculations have clearly shown that the orientation of antiferromagnet spins also exhibits hysteresis between clockwise and counterclockwise rotations. This furnishes an interpretation of the macroscopic behavior of the ferromagnetic layer in terms of the thermally driven evolution of the magnetic state of the antiferromagnet layer. 28 degrees for t AFM =10 nm. As shown in Fig. 1(a), H E has almost the same angular dependence for CW and CCW rotations, which will be analyzed below.As discussed below, the results in Fig. 1 are caused by the hysteresis of ADEB. In order to verify this, firstly another CW rotation was measured directly after one cycling of CW and CCW rotations. It is found that the ADEB for the second CW rotation is almost the same as that of the first. Secondly, ∆φ H is shown to be independent of the increment of φ H between neighboring hysteresis loops. Finally, the ADEB of CW and CCW rotations was measured within different φ H regimes. As shown in Fig. 2(a), the angular dependence of m y−AVE is reversible for CW and CCW rotations for small φ H ranges. However, it is irreversible for larger φ H regimes, as shown in Fig. 2(b). Unambiguously, the hysteretic behavior of the ADEB is demonstrated. The hysteresis of the ADEB can be explained qualitatively. Consider a hysteresis loop for the FM layer, i.e.,Calculations show that the average orien- The discrepancy of H E hysteresis between measured ( Fig. 1(a)) and calculated ( Fig. 4(a)) results can be explained as

Emergence of noncollinear anisotropies from interfacial magnetic frustration in exchange-bias systems

“…In general, rotation processes are more relevant in one branch of the hysteresis loop, in which a larger density of domains during irreversible domain nucleation processes is also observed. 25,28,29,35,36 For some systems, rounded transitions in M ʈ and larger M Ќ values are found in the descending branch, 20,21,[25][26][27][28][34][35][36] where the field is applied parallel to the exchange-bias direction, while other systems display the opposite behavior. [21][22][23][24][25][29][30][31][32][33] Our results indicate that this discrepancy is related to the difference between a collinear and a noncollinear anisotropy case.…”

“…Asymmetries in the magnetization reversal have been observed for many FM/AFM systems with both in-plane [20][21][22][23][24][25][26][27][28][29][30][31][32][33][34] and perpendicular 35,36 anisotropy for the FM layer. In general, rotation processes are more relevant in one branch of the hysteresis loop, in which a larger density of domains during irreversible domain nucleation processes is also observed.…”

The influence of ultrathin Cu interlayer in NiFe/IrMn interface on rotation of the magnetic moments

“…And the crystalline degree of AFM layer has close connection with anisotropy energy barrier which will increase with the improving of the AFM crystalline degree. So the worse IrMn crystalline degree does not increase the anisotropy energy barrier but decrease it, which will facilitate the pinning direction inclines to unstable state [18].…”

Antiferromagnetic layer thickness dependence of the coercivity of the ferromagnetic/antiferromagnetic two‐phase system

“…Nevertheless, some properties of these systems are not well explained. Gao et al found that the coercivity of a FM/AFM coupling system increases with the AFM layer thickness first, and decreases after a peak, and then tends to saturate. This kind of peak in the coercivity curve has also been reported by other authors and its origin is currently not satisfactorily explained.…”