Ab initio investigations of magnetic properties of ultrathin transition ...

4.3 3d-Monolayers on Rh(111) Substrate: 67
presented in figure 4.15 and compared to the 3d/Rh(001) results.
Figure 4.14: FM (left) and RW-AFM (right) unit cells of hexagonal lattices.
Δd 12 [%]
Δd 23 [%]
0
−2
−4
−6
−8
−10
−12
8
6
4
2
0
−2
FM
3d
Rh(I)
1 ML 3d on
Rh(001)
Rh(111)
V Cr Mn Fe Co Ni
RW-AFM
3d
Rh(I)
1 ML 3d on
Rh(001)
Rh(111)
V Cr Mn Fe Co Ni
Figure 4.15: Change of the first and second interlayer spacing, Δd12 and Δd23, respectively,
for 3d TM monolayers on Rh(111) (circles) and Rh(001) (squares). Solid (dashed) lines
indicate the FM (RW-AFM) results. The corresponding changes are given with respect to
the substrates bulk interlayer spacing along [111] ([001]), which is 2.21 ˚A(1.91 ˚A).
From figure 4.15 we notice that the smallest Δd12 inward FM relaxation of the 3d
monolayer occurs again for Mn on Rh(111), as it is for the case on Rh(001). This is due
to the strong magneto-volume effect of Mn, which is reflected in the large Mn magnetic
moments, which compensate most efficiently the strong inward relaxation caused by the
larger Rh lattice constant. For the close packed (111) surfaces, the unit cell volume is
smaller, therefore the inter-atomic distances will get smaller, and then their relaxations
are expected to be smaller than in the (001) surface. This can bee seen in our comparison
between 3d/Rh(111) and 3d/Rh(001) FM and AFM relaxations. We notice that there is
only small difference of Fe FM relaxations between Rh(001) and Rh(111), compared to
almost similar change for Mn, Co and Ni FM relaxations, although Fe has larger magnetic
moments than Co and Ni on Rh(111) as well as on Rh(001). This indicates that there are
other factors than the magneto-volume effect, which might arise from the hybridization
effects between Fe-Rh(111) and Fe-Rh(001) in a similar manner.