Faculty of Physics and Computer Science, AGH University of Science and Technology, al. A. Mickiewicza 30, 30-059 Kraków, Poland.
J Phys Condens Matter. 2010 Nov 3;22(43):435403. doi: 10.1088/0953-8984/22/43/435403. Epub 2010 Oct 11.
(57)Fe site Mössbauer spectroscopy (MS) was used to investigate the dynamics of (57)Fe atoms embedded in a chromium lattice as impurities. From the Mössbauer spectra recorded in the temperature range of 80-350 K, a temperature dependence of the Lamb-Mössbauer factor, f, was determined. The latter revealed an unusual dynamics of (57)Fe atoms, namely a harmonic mode below T≈145 K with a characteristic effective Debye temperature Θ(eff) = 190.2 K and a strongly anharmonic one above T≈145 K. The latter mode exists in two clearly defined temperature intervals with significantly different Θ(eff) values, namely (i) ∼155 K for ∼145 K ≤ T ≤ ∼240 K and the record-high anharmonic coefficient ε = -25.8 × 10(-4) K(-1), and (ii) ∼151 K for T ≥ ∼240 K with ε = -14 × 10(-4) K(-1). Based on Visscher's theory, the record-low value of the relative binding force constant for Fe atoms was determined as 0.0997 for the harmonic regime. It is suggested that the unusual dynamics observed in this study might be related to the underlying spin-, charge- and strain-density waves of chromium.
(57)Fe 原子的穆斯堡尔谱（MS）被用来研究铬晶格中作为杂质的嵌入 (57)Fe 原子的动力学。从 80-350 K 的温度范围内记录的穆斯堡尔谱中，确定了拉曼-穆斯堡尔因子 f 的温度依赖性。后者揭示了 (57)Fe 原子异常的动力学，即在 T≈145 K 以下具有特征有效德拜温度 Θ(eff)=190.2 K 的谐波模式，以及在 T≈145 K 以上的强烈非谐波模式。后者模式存在于两个明显不同的温度间隔内，具有明显不同的 Θ(eff) 值，即 (i) ∼155 K 对于 ∼145 K ≤ T ≤ ∼240 K 和记录高的非谐系数 ε = -25.8×10(-4) K(-1)，以及 (ii) ∼151 K 对于 T ≥ ∼240 K 和 ε = -14×10(-4) K(-1)。基于 Visscher 的理论，确定了在谐波区域中 Fe 原子相对结合力常数的记录低值为 0.0997。有人认为，在这项研究中观察到的异常动力学可能与铬的潜在自旋、电荷和应变密度波有关。
