Characterization of low-energy magnetic excitations in chromium
Characterization of low-energy magnetic excitations in chromium
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DOI：
10.1103/physrevb.70.144413
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发表时间：
2003-12
影响因子：
3.7
通讯作者：
H. Hiraka;P. Boni;K. Yamada;S. Park;S. Lee;G. Shirane
中科院分区：
文献类型：
--
作者：
H. Hiraka;P. Boni;K. Yamada;S. Park;S. Lee;G. Shirane
在横向极化的自旋密度波相中，用single-${\mathbf{Q}}_{\ifmmode\pm\else\textpm\fi{}}$晶体进行非弹性中子散射，研究了铬的低能激发，即芬奇-伯克(FB)模。恒动量转移扫描表明，能谱由两个分量组成，即色散的FB模和几乎与能量无关的截面。最值得注意的是，我们发现FB模的光谱分别在$140\phantom{0.3em}{0ex}\mathm{K}$=(0，0，0.98)$和$\mathbf{q}=(0，0，1.02)$附近出现两个峰。这是令人惊讶的，因为铬以中心对称的体心立方结构结晶。这些能谱的不对称性随着温度的升高而减小。此外，观测到的磁峰强度与f{q}无关，这表明在Fb模的上下两个模之间存在谱权转移。与能量无关的截面只局限在无公度峰之间，并随着温度的升高而迅速发展。
The low-energy excitations of Cr, i.e., the Fincher-Burke (FB) modes, have been investigated in the transversely polarized spin-density-wave phase by inelastic neutron scattering using a single-${\mathbf{Q}}_{\ifmmode\pm\else\textpm\fi{}}$ crystal with a propagation vector ${\mathbf{Q}}_{\ifmmode\pm\else\textpm\fi{}}$ parallel to [001]. The constant-momentum-transfer scans show that the energy spectra consist of two components, namely dispersive FB modes and an almost energy-independent cross section. Most remarkably, we find that the spectrum of the FB modes exhibits one peak at $140\phantom{\rule{0.3em}{0ex}}\mathrm{K}$ near $\mathbf{Q}=(0,0,0.98)$ and two peaks near $\mathbf{Q}=(0,0,1.02)$, respectively. This is surprising because Cr crystallizes in a centrosymmetric bcc structure. The asymmetry of those energy spectra decreases with increasing temperature. In addition, the observed magnetic peak intensity is independent of $\mathbf{Q}$, suggesting a transfer of spectral weight between the upper and lower FB modes. The energy-independent cross section is localized only between the incommensurate peaks and develops rapidly with increasing temperature.