SPXAS calculation

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SPXAS

For antiferromagnets, the XMCD should be zero, and a measure of the spin-up and spin-down signals can be accomplished using SPXAS. SPXAS is a technique where you measure the spin-up and spin-down signal by measuring intensity of two spin-split Kβ lines. This corresponds to measuring spin-order relative to the spin on the absorber (not relative to the external magnetic field as in XMCD). As an example, let us look at the Mn K edge of antiferromagnetic MnF2. Our calculations agree well with experiment in the EXAFS region.

Here is an example input file (caution: this input file may not work for later versions of feff in which the relative spin amplitudes must be specified using the 7th column of the POTENTIALS card) for MnF2:

TITLE MnF2 (rutile) cassiterite (Wykoff)

HOLE 1 1.0 1=k edge, s0^2=1.0

SPIN 2
CONTROL  1    1    1    1    1    1
PRINT    0    0    0    2    0    4
EXCHANGE 0  0.0 0.0
CORRECTIONS 0.0 0.0

RPATH 10.0
XANES

PCRITERIA 0.8 40.0
*CRITERIA curved plane
CRITERIA  0.0 0.0
*DEBYE   temp debye-temp
 DEBYE   300 350
NLEG    4

POTENTIALS
*   ipot  z  label
      0  25   Mnup
      1  9    F
      2  25   Mnup
      3  25   Mndown

ATOMS
  0.0000   0.0000   0.0000  0  Mnup     0.0000
  1.4864   1.4864   0.0000  1  F        2.1021
 -1.4864  -1.4864   0.0000  1  F        2.1021
  0.9503  -0.9503   1.6550  1  F        2.1319
  0.9503  -0.9503  -1.6550  1  F        2.1319
 -0.9503   0.9503   1.6550  1  F        2.1319
 -0.9503   0.9503  -1.6550  1  F        2.1319
  0.0000   0.0000  -3.3099  3  Mndown   3.3099
  0.0000   0.0000   3.3099  3  Mndown   3.3099
 -3.3870   1.4864   0.0000  1  F        3.6988
  3.3870  -1.4864   0.0000  1  F        3.6988
  1.4864  -3.3870   0.0000  1  F        3.6988
 -1.4864   3.3870   0.0000  1  F        3.6988
  2.4367   2.4367  -1.6550  2  Mnup     3.8228
 -2.4367  -2.4367  -1.6550  2  Mnup     3.8228
  2.4367  -2.4367  -1.6550  3  Mndown   3.8228
 -2.4367  -2.4367   1.6550  3  Mndown   3.8228
 -2.4367   2.4367  -1.6550  3  Mndown   3.8228
  2.4367   2.4367   1.6550  3  Mndown   3.8228
  2.4367  -2.4367   1.6550  2  Mnup     3.8228
 -2.4367   2.4367   1.6550  2  Mnup     3.8228
  ...
END

Calculation Strategies and Examples

Spin dependent calculations

  1. General description
  2. XMCD
  3. SPXAS

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