Valence Of Sm Ions Research Articles

Magnetic and Thermal Properties of SmRh2Zn20 Single Crystal

The magnetization, magnetic susceptibility, and specific heat of the single crystalline sample SmRh$_2$Zn$_{20}$ were measured. The valence of Sm ions in SmRh$_2$Zn$_{20}$ was found to be trivalent. No evidence of valence fluctuations was detected. SmRh$_2$Zn$_{20}$ is an antiferromagnet with $T_{\rm N}=$ 2.46 K. The observed $C(T,H)$ curves showed that $T_{\rm N}$ splits into two in the external field $H$ along the [001] and [101]directions. On the other hand, $T_{\rm N}$ in $H$ along the [111] direction did not split, decreasing to 2.20 K at $H=7$ T. At 2 K, the magnetization $M_{111}$ in $H$ along the [111] direction increased linearly with increasing field, while $M_{001}$ and $M_{101}$ deviated upward slightly from the linear dependence. We analyzed the observed magnetic and thermal properties of SmRh$_2$Zn$_{20}$ taking into account the crystalline-electric-field effect, the Zeeman energy, and the exchange interaction. The theoretical calculation well reproduced the experimental $\chi(T)$, $M(H)$, $C(T,H)$ and $T_{\rm N}(H)$. The sublattice magnetic moments are expected to be along the $\langle 111\rangle$ direction below $T_{\rm N}$ at $H=0$ T. Variations of the magnetic structures induced by the external magnetic fields in a narrow temperature region around $T_{\rm N}$ are inferred on the basis of theoretical calculations.

Investigation of the electronic structure in [formula omitted] by means of MCD measurements

X-ray absorption and magnetic circular dichroism measurements were carried out around the Sm M 4 , 5 and Co L 2 , 3 edges on SmCo 3 B 2 . The valence of Sm ions in SmCo 3 B 2 is trivalent. Co-3d electrons of SmCo 3 B 2 are more localized than those of pure Co metal and SmCo 5 . The component of the orbital magnetic moment of Co-3d electrons in SmCo 3 B 2 enhances in comparison with that of pure Co metal.

Study of the electronic structure of SmNiC 2 by X‐ray Magnetic Circular Dichroism measurements

We investigated the electronic structure of SmNiC2 by using X-ray absorption spectroscopy (XAS) and magnetic circular dichroism (MCD). The XAS and MCD measurements were performed around Sm L 2,3-edges and Ni K -edge. The element selective magnetic hysteresis curves were measured around Sm L 2,3-edges and Ni K -edge. The XAS spectrum showed a single peak around Sm L 2,3-edges. The valence of Sm ions in SmNiC2 is a little smaller than trivalent. The MCD signals were clearly observed around all absorption edges below the Curie temperature. We concluded that Ni atoms in SmNiC2 have a finite magnetic moment by analyzing the spectrum at Sm L 3-edge. The shape of ESMH loops were different from the hysteresis loop measured by a SQUID magnetometer. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

Photoemission Spectroscopy of Sm4As3Using Soft and Hard X-rays

The bulk and surface electronic structures of Sm 4 As 3 have been investigated by hard and soft X-ray photoemission spectroscopies (PESs). PES with a wide range of photon energies ( h ν's) between 220 and 2450 eV demonstrates the absence of valence mixing in both high- and low-temperature phases, that is, the valence of Sm ions is definitely trivalent in the bulk and divalent on the surface. Atomic multiplet calculations taking into account the bulk and surface spectral weights at each h ν well reproduce the experimental valence band PES and Sm 3 d core-level spectra, supporting the valence difference between bulk and surface in Sm 4 As 3 .

Thermal Conductivity of Sm 3 S 4 System with Mixed Valence Sm Ions

The thermal conductivity (κ) and electrical resistivity (ρ) of mixed-valence compound Sm3S4 have been measured in the temperature range 5 to 300 K. The present results and those presented previously [1] for the thermal conductivity between 80 to 850 K are interpreted in terms of the temperature-dependent fluctuating valence of Sm ions. Sm3S4 crystallizes in the cubic Th3P4 structure, and the cations with different valences occupy equivalent lattice sites. Divalent and trivalent Sm ions are randomly distributed in the ratio of 1:2 over all possible crystallographic cation positions (Sm2+ 2Sm3+ 2S2− 4). The behavior of the Sm3S4 lattice thermal conductivity κ ph is extraordinary since valences of Sm ions are fluctuating (Sm3+→Sm2+) with a temperature dependent frequency. In the interval 20 to 50 K (low “hopping” frequencies), κ ph of Sm3S4 varies as κ ph ∼T −1 (it is similar to materials with static distribution of cations with different valences): at 95 to 300 K (average “hopping” frequencies 107 to 1011 Hz), κ ph changes as κ ph ∼T −0.3 (it is similar to materials with defects). Defects in Sm3S4 appear because of local strains in the lattice by the electrons hopping from Sm2+ ions (with big ionic radii) to Sm3+ ions (with small ionic radii) and back (Sm2+→Sm3+), at T>300 K (high “hopping” frequencies), κ ph becomes similar to materials with homogenous mixed valence states [1].

Physical properties of antiferromagnetic ternary compound SmPd 2Al 3

Measurements of electrical resistivity, magnetic susceptibility and specific heat have been performed on a new ternary compound SmPd 2Al 3. The results indicate that the valence of Sm ions is almost trivalent and that SmPd 2Al 3 has a complicated magnetic phase diagram below 12 K.

Sm M4,5 Spectra of Metallic Samarium and Samarium Hexaboride

The samarium M 4,5 emission and absorption spectra of Sm-metal and SmB 6 were studied. It was found that the spectra of these materials are in close resemblance. The emission spectra obtained by higher excitation energies exhibit appreciable effects of self-absorption because of the presence of absorption peaks in the same energy region. Contrary to the case of the L -edge absorption the M 4,5 absorption of SmB 6 showed no distinct indication of the difference due to Sm 3+ and Sm 2+ ions. The spectra of Sm 2 O 3 , SmS and SmSe were also studied, and it was observed that they have common features among themselves regardless of the difference in the valence of Sm ions.