Magnetic dichroisms in absorption and photoemission for magnetic characterization in x-ray photoelectron emission microscopy

Abstract

Magnetic contrast for the operation of a photoelectron emission microscope (PEEM) with synchrotron radiation is provided by magnetic dichroisms. Besides the most frequently employed magnetic dichroism, magnetic circular dichroism in x-ray absorption spectroscopy, energy filtering of photoemitted electrons allows one to also use magnetic dichroisms in photoelectron emission as complementary contrast mechanisms. We demonstrate that it is possible to obtain magnetic contrast in photoemission using PEEM equipped with a simple retarding field electron energy analyzer. Magnetic domain images of an ultrathin film of 10 atomic monolayers of Fe on W(001), obtained by three, different contrast mechanisms (circular magnetic dichroism in x-ray absorption, circular magnetic dichroism in Fe valence band photoemission, and linear magnetic dichroism in Fe 3p photoemission) are presented and compared

Quantitative microscopy of magnetic domains in Fe(100) by core-level x-ray photoelectron spectroscopy

“…While MCD is sensitive to the longitudinal component of the magnetization, MLDAD senses the transverse component of the magnetization. 12, 13 We will show that both types of dichroisms can be calculated from just two measurements taken with left and right circular polarization, thus allowing for a quantitative evaluation of magnetization components in a single experimental step. We have chosen as an example a partly recrystallized Fe͑100͒ single crystal at which the well-known simple domain structure within the nonrecrystallized part can be used for normalization in order to demonstrate the numerical evaluation procedure of magnetization patterns.…”

“…In our case, the photon energy is chosen high enough to create excitations into states about 100 eV above E F and thus reduces the influence of asymmetries in the excited states around E F . The magnetic dichroism occurring in direct photoemission from core or valence-band initial states [11][12][13] is then used as a magnetic contrast mechanism for imaging magnetic domains. In addition, directly emitted pho-toelectrons carry information on the chemical state of the specified element.…”

“…Depending on the polarization of the incident photons, two types of magnetic dichroism, i.e., magnetic circular ͑MCD͒ 14-18 and magnetic linear ͑MLDAD͒ dichroism, [18][19][20][21][22][23][24][25] in the angular distribution of photoelectrons can be distinguished. [11][12][13] A few experiments have been carried out that use dichroism in core-level photoemission as the contrast mechanism for imaging of magnetic domains. 13,26,27 In this work, we demonstrate the possibility to study magnetization structures by only considering core-level x-ray photoelectron spectroscopy ͑XPS͒ images on a reasonable time scale.…”

“…[11][12][13] A few experiments have been carried out that use dichroism in core-level photoemission as the contrast mechanism for imaging of magnetic domains. 13,26,27 In this work, we demonstrate the possibility to study magnetization structures by only considering core-level x-ray photoelectron spectroscopy ͑XPS͒ images on a reasonable time scale. While MCD is sensitive to the longitudinal component of the magnetization, MLDAD senses the transverse component of the magnetization.…”

Resonant soft x-ray techniques to resolve nanoscale magnetism

“…Rather than using spin-polarization detection, however, magnetic contrast is gained through the XMCD or XMLD effects on the secondary emission, requiring incident tunable soft x-rays of suitable polarization [106,107,108,109]. Such photo-emission electron microscopes (PEEMs) have routine spatial resolution of ~ 50 nm set by chromatic aberrations of imaging secondary electrons.…”