Atomic-scale depth selectivity of soft x-ray resonant Kerr effect

Abstract

By the use of resonant soft x-ray Kerr rotation measurements with its varying incident angle and energy, we observed various shifts of the exchange bias field of a 3.5-nm-thick Co layer in oppositely exchange-biased Ni81Fe19/Fe50Mn50/Co/Pd films. The results in conjunction with their model simulations clearly reveal that the measurements enable one to resolve varying magnetization with depth in the individual magnetic layers of such a multicomponent ultrathin layered structure on the atomic scales. Significant interference effects combined with penetration depth of resonant soft x rays, which are closely associated with their absorptive and refractive contributions, offer remarkably different depth sensitivities into the Kerr effects depending on grazing angle and resonance energy.

Soft x-ray resonant Kerr rotation measurement and simulation of element-resolved and interface-sensitive magnetization reversals in a NiFe∕FeMn∕Co trilayer structure

“…The negative and positive shifts of the Fe loops are exactly the same as H eb = −100 and +120 Oe for the interfacial Co and the NiFe exchange bias, respectively. 12,13 It is evident from the negative side Fe loops that the interfacial UC Fe adjacent to the Co layer is F in character. Also, it is clear that this UC interfacial region is coupled strongly to the exchange-biased Co reversal, consequently switchable.…”

“…These novel properties can be utilized to resolve element-specific and depthvarying M reversals in multicomponent multilayer films. Details for these measurements 16,17 and its related depth sensitivity 13,14 have been reported elsewhere. Figure 1͑c͒ shows the resultant hysteresis loops of Co-, Ni-, and Fe-resolved M reversals, measured via their element enhanced contrasts of K at the chosen values of h as noted.…”

“…12 To investigate element-resolved and depth-sensitive M reversals from that sample structure, we utilize an element-specific and depth-sensitive probe using synchrotron soft x rays and interpret those data with the help of elaborate model calculations. 13,14 The soft x-ray resonant magneto-optical K measurements were carried out by varying and h in the vicinity of the resonance regions of individual magnetic elements. Figure 1͑a͒ displays a geometry for the soft x-ray resonant K measurements using linearly s-polarized x rays at a chosen value of and a tunable multilayer linear polarizer that senses the rotation of the plane of linear polarizations accompanying magnetic circular birefringence.…”

Soft x-ray polarizer for optical productions of any orthogonal state of the linear and circular polarization modes

“…[1][2][3][4][5][6][7] This is because the individual orthogonal states of the linear or circular polarization mode are extremely sensitive differently to the transverse, longitudinal, and polar orientations of magnetizations in the vicinity of the absorption edges for various 3d transition metals or 4f rare earths in the soft x-ray range roughly from 50 eV to 2 keV. 8 Therefore, special insertion devices such as an elliptically polarizing undulator ͑EPU͒ have been facilitated in order to effectively produce high photon flux, energy tunable, circular, or linear polarization eigenmodes.…”

Soft x-ray resonant magneto-optical Kerr effect as a depth-sensitive probe of magnetic heterogeneity: Its application to resolve helical spin structures using linear p polarization

“…4,7,8 In addition, a depth-varying exchange-bias behavior in an ultrathin Co layer, sandwiched between a Pd capping layer and an antiferromagnetic FeMn layer, was observed in an earlier work. 9 Visible light or x-ray magneto-optical (MO) effects, such as the Kerr rotation K and ellipticity K , have been widely used to investigate a rich variety of magnetic states in magnetic heterostructures, because the MO effect is significantly sensitive to the small amount of magnetic moments in their magnitude and direction. [10][11][12][13][14][15][16] In particular, a synchrotron x-ray MO spectroscopy is emerging as a powerful cuttingedge technique, becoming a popular method to investigate the various magnetic properties being associated with nanostructures because of its several unique characteristics such as element specificity, magnetic sensitivity, and large resonant enhancement in the vicinity of the absorption edges, as well as the ongoing growths in the measurement and/or analysis techniques.…”