Abstract
Acoustic surface-magnon spectra are calculated for semi-infinite ferro- and antiferromagnets, where spins are coupled via exchange interactions both with nearest neighbors (J1) and with next-nearest neighbors (J 2). It is found that, when the parameter α=J 2/|J1| lies in certain intervals, the surface-magnon frequency is negative or imaginary, although the bulk-magnon frequencies remain real and positive. This condition indicates that the uniform ferro- or antiferromagnetic spin arrangement is not stable. For several cases of this type, it is shown that a nonuniform spin arrangement, characterized by a rearrangement of spins in the surface region, has a lower classical spin-ordering energy than the uniform state, and hence is stable. In various cases, various different arrangements of surface spins are found to be stable, including a helical arrangement, in which spins in the surface region are ordered with helical symmetry while bulk spins are in an antiferromagnetic state.
| Original language | English |
|---|---|
| Pages (from-to) | 738-748 |
| Number of pages | 11 |
| Journal | Journal of the Physical Society of Japan |
| Volume | 42 |
| Issue number | 3 |
| Publication status | Published - Mar 1977 |
| Externally published | Yes |
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ASJC Scopus subject areas
- Physics and Astronomy(all)
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Surface magnons and surface spin arrangements in Heisenberg magnets with two kinds of exchange interactions. / Harada, Isao; Nagai, Ojiro.
In: Journal of the Physical Society of Japan, Vol. 42, No. 3, 03.1977, p. 738-748.Research output: Contribution to journal › Article
}
TY - JOUR
T1 - Surface magnons and surface spin arrangements in Heisenberg magnets with two kinds of exchange interactions
AU - Harada, Isao
AU - Nagai, Ojiro
PY - 1977/3
Y1 - 1977/3
N2 - Acoustic surface-magnon spectra are calculated for semi-infinite ferro- and antiferromagnets, where spins are coupled via exchange interactions both with nearest neighbors (J1) and with next-nearest neighbors (J 2). It is found that, when the parameter α=J 2/|J1| lies in certain intervals, the surface-magnon frequency is negative or imaginary, although the bulk-magnon frequencies remain real and positive. This condition indicates that the uniform ferro- or antiferromagnetic spin arrangement is not stable. For several cases of this type, it is shown that a nonuniform spin arrangement, characterized by a rearrangement of spins in the surface region, has a lower classical spin-ordering energy than the uniform state, and hence is stable. In various cases, various different arrangements of surface spins are found to be stable, including a helical arrangement, in which spins in the surface region are ordered with helical symmetry while bulk spins are in an antiferromagnetic state.
AB - Acoustic surface-magnon spectra are calculated for semi-infinite ferro- and antiferromagnets, where spins are coupled via exchange interactions both with nearest neighbors (J1) and with next-nearest neighbors (J 2). It is found that, when the parameter α=J 2/|J1| lies in certain intervals, the surface-magnon frequency is negative or imaginary, although the bulk-magnon frequencies remain real and positive. This condition indicates that the uniform ferro- or antiferromagnetic spin arrangement is not stable. For several cases of this type, it is shown that a nonuniform spin arrangement, characterized by a rearrangement of spins in the surface region, has a lower classical spin-ordering energy than the uniform state, and hence is stable. In various cases, various different arrangements of surface spins are found to be stable, including a helical arrangement, in which spins in the surface region are ordered with helical symmetry while bulk spins are in an antiferromagnetic state.
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M3 - Article
AN - SCOPUS:3342920652
VL - 42
SP - 738
EP - 748
JO - Journal of the Physical Society of Japan
JF - Journal of the Physical Society of Japan
SN - 0031-9015
IS - 3
ER -