How Antiferromagnetism Drives the Magnetization of a Ferromagnetic Thin Film to Align Out of Plane

Abstract

Interfacial moments of an antiferromagnet are known for their prominent effects of induced coercivity enhancement and exchange bias in ferromagnetic-antiferromagnetic exchange-coupled systems. Here we report that the unpinned moments of an antiferromagnetic face-centered-cubic Mn layer can drive the magnetization of an adjacent Fe film perpendicular owing to a formation of intrinsic perpendicular anisotropy. X-ray magnetic circular dichroism and hysteresis loops show establishment of perpendicular magnetization on Fe/Mn bilayers while temperature was decreased. The fact that the magnitude of perpendicular anisotropy of the Fe layer is enhanced proportionally to the out-of-plane oriented orbital moment of the Mn unpinned layer, rather than that of Fe itself, gives evidence for the Mn unpinned moments to be the origin of the established perpendicular magnetization.

Monte Carlo simulations of the fcc kagome lattice: Competition between triangular frustration and cubic anisotropy

“…21 The present case is different in that the usual kagome degeneracy of spins state with magnetic representation 2T 1 + T 2 of the octahedral point group is fully removed. 22 The development of a finite magnetic moment along the [111] direction as a consequence of anisotropy along with the expected in-plane canting of the spins on the top layer of the antiferromagnet in the presence of a ferromagnetic layer 17 are expected to be important to describe the exchange bias seen in IrMn 3 . For this purpose, simulations are planned to study thin films of the fcc kagome structure and to also include exchange coupling to a ferromagnetic layer.…”

“…Some studies also suggest that exchange bias is enhanced if this moment is perpendicular to the plane of the film. 16,17 An essential requirement for technological applications is that the AF layer magnetically orders well above room temperature.…”

Evidence for asymmetric rotation of spins in antiferromagnetic exchange-spring

“…As the common AFM materials used widely in magnetic tunnel junctions, chemicallydisordered FeMn and IrMn (L1 2 -IrMn 3 ) have a noncollinear magnetic structure in the bulk, making the spins hard to identify, let alone manipulate [11,[16][17][18]. It is worth pointing out that beyond the current passive role of AFM in pinning FM, spins in ultrathin AFM layer could also be motivated by the neighbored FM, leading to a twisted exchange-spring in AFM, accompanied by uncompensated moments at the interface [12,13,19,20]. Direct recognition of the exchange-spring is in great demand because it is essential for manipulating AFM moments as well as realizing the functionality of AFM layers [21].…”

“…After clarifying the spin arrangements in the whole AFM exchange-spring, we now turn towards the interfacial behaviors, which are also significant for the coupling between FM/AFM. In contrast to XMLD experiments, which concentrate on the spin directions in the exchangespring, XMCD could be used to characterize the ferromagnetism in FM, together with the uncompensated moments in AFM at the interface [12,20]. Tiny magnetic signals of the interfacial Fe and Mn spins could be separated from large signals of the Co FM layer [12,20], taking advantage of the element specificity.…”

Variation of blocking temperatures for exchange biased CoO/Co/Ge(100) films

“…EB is sensitive to AFM/FM interfacial conditions and therefore atomic-scale roughness, magnetic uncompensated AFM surface, crystallographic order, and strain effects may influence its performance. [1][2][3][4][5][6][7] For the last decade, EB has been used in commercial applications such as magnetic spin-valve sensor and magnetic random access memories. [8][9][10][11] As an example for thermally assisted-MRAM (TA-MRAM), a large exchange bias field (H E ), a reduced coercive force (H C ), and well-defined temperature variations of both characteristic fields are required.…”