Spin-polarized Photoelectron Diffraction Research Articles

Spin-polarized photoelectron diffraction: A new probe of short-range magnetic order (invited) (abstract)

It has recently been pointed out theoretically and subsequently observed experimentally that core-level multiplet splittings can be used to yield a spin-polarized form of photoelectron diffraction (SPPD). This internally referenced source of electrons that are highly polarized with both orientations of spin thus eliminates the need for an external spin detector, permits studying both ferromagnetic and antiferromagnetic specimens, and can, in principle, detect short-range magnetic or for temperatures above the Curie or Néel temperature. In the first measurements of this type on the antiferromagnet KMnF3, an abrupt loss of short-range order at a transition temperature considerably above the bulk Néel temperature of the material was observed. More recent theoretical diffraction calculations have pointed out several ways in which SPPD should permit deriving unique information on short-range spin-order structures at and near the surfaces of magnetic materials. New experimental results have also been obtained for the antiferromagnet MnO. This paper will discuss these new developments, will review the advantages and disadvantages of SPPD, and also will consider some interesting future directions of investigation.

Summary Abstract: Spin-polarized photoelectron diffraction: A new probe of surface magnetic order

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Summary Abstract: Spin-polarized photoelectron diffraction from magnetically ordered solids and surfaces

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Spin-polarized photoelectron diffraction from magnetically-ordered solids and surfaces

We report the first experimental observation of Spin-Polarized Photoelectron Diffraction (SPPD), an effect which shows considerable promise for studying short-range order in magnetic solids and surfaces. The detection of photoelectron spin polarization in this experiment is provided by 3s-level multiplet splittings in 3d metals and their compounds; thus no external spin detector is required. Measurements on antiferromagnetic KMnF 3 show spin asymmetries of as high as 17% due to short-range order.

Observation of spin-polarized photoelectron diffraction.

We report the first observation of spin-polarized photoelectron diffraction in core-level emission from antiferromagnetic KMn${\mathrm{F}}_{3}$. The Mn $3s$ multiplet splitting provides an internal source of polarized electrons, and spin-polarized photoelectron diffraction effects of up to 17% are seen in the $\frac{^{5}S}{^{7}S}$ intensity ratio. These effects are found to be very sensitive to both emission direction and temperature. Short-range antiferromagnetic order is found to persist up to approximately 3 times the N\'eel temperature.

Spin-polarized photoelectron diffraction.

The use of multiplet-split $s$ levels in magnetic atoms or ions for spin-polarized photoelectron diffraction or extended x-ray absorption fine-structure experiments is discussed. Over the range 50-500 eV, spin-dependent scattering factors for ${\mathrm{Mn}}^{2+}$ show exchange-induced asymmetries of as high as 8%, with significantly larger effects expected for forward scattering as compared to backscattering. Single-scattering-cluster photoelectron diffraction calculations for Mn $3s$ emission from antiferromagnetic KMn${\mathrm{F}}_{3}$ show net effects ranging from 8% at 50 eV to 1% at 400 eV.