SPXAS calculation
From FEFF
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
- General description
- XMCD
- SPXAS
