The temperature dependence of nuclear resonant X-Ray spectra of magnetic iron and cementite
The temperature dependence of nuclear resonant X-Ray spectra of magnetic iron and cementite
复制标题
DOI：
10.1007/s10751-021-01750-6
复制
发表时间：
2021-12
影响因子：
--
通讯作者：
L. Mauger;S. H. Lohaus;B. Fultz
中科院分区：
文献类型：
--
作者：
L. Mauger;S. H. Lohaus;B. Fultz
从低温到居里温度，通过核共振非弹性X射线散射（NRIXS）测量了bcc 57 Fe的声子态密度（DOS），并测量了57 Fe3C的声子态密度。用核前向散射（NFS）方法测定了57Fe3C的磁化状态。声子态密度随磁化强度的变化进行了评估，发现磁化强度的温度依赖性与声子频率的非准谐波位移之间存在线性关系。根据非简谐声子的准谐波近似（QHA），发展了一个磁准谐波理论来解释声子频率如何随磁化强度的变化而改变。形式主义很好地解释了体心立方铁和菱铁矿的自由能测量和QHA预测之间的差异。磁格吕奈森参数的物理起源仍然是一个挑战。
From low temperatures through the Curie temperatures, the phonon density of states (DOS) was measured for bcc57Fe, and the partial phonon DOS was measured for cementite,57Fe3C, by nuclear resonant inelastic x-ray scattering (NRIXS). Nuclear forward scattering (NFS) was used to determine the state of magnetization of57Fe3C. The changes in phonon DOS with magnetization were assessed, and a linear relationship was found between the temperature dependences of the magnetization and the non-quasiharmonic shifts of phonon frequencies. Following the quasiharmonic approximation (QHA) for non-harmonic phonons, a magnetic quasiharmonic theory is developed to account for how phonon frequencies are altered by changes in magnetization. The formalism explains well the discrepancy between the free energy measurements and predictions of the QHA for both bcc iron and cementite. The physical origin of the magnetic Grüneisen parameters remains a challenge.