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Thermoelectric conversion devices based on group IV semiconductor elements can improve conversion efficiency by reducing the thermal conductivity of the material. In particular, it is known that introducing Sn into the system can dramatically reduce the conductivity. It has been experimentally shown that the thermal conductivity of polycrystalline Ge and polycrystalline Si1−xGex can be reduced by introduction of Sn. However, there is no experimental report on the effect of Sn atoms on the phonons responsible for thermal conduction. In this study, we investigated the mechanism of thermal conductivity reduction due to the introduction of Sn by inelastic x-ray scattering measurements on a Ge1−xSnx single-crystalline thin film with 9% Sn composition. The phonon dispersion of Ge1−xSnx was obtained as a result of the measurements, and the slope of the acoustic mode in the phonon dispersion curve of Ge1−xSnx was smaller than that of Ge. The phonon group velocity is expressed as the slope of the dispersion curves of the acoustic mode. Therefore, it was suggested that the reduction of the phonon group velocity by the introduction of Sn partly contributes to the reduction of the thermal conductivity of Ge1−xSnx. Local vibration mode (LVM), which was independent of wavenumber, was also observed in the low-energy region, and we attribute the origin to the local structure of Sn–Sn pairs formed in Ge1−xSnx. Such LVM has also been reported in bulk single- and polycrystalline Si1−xGex and polycrystalline Si1−x−yGexSny and is considered to influence the thermal conductivity reduction.

In an antiferromagnetic zigzag chain, competition between the nearest and next-nearest neighbor interactions could give rise to magnetic frustration. Magnetic semiconductors RAgSe2 (R = Ho, Er, Tm, and Yb) crystallize in the ErAgSe2-type orthorhombic structure, where the R ions form a zigzag chain along the orthorhombic a-axis. The magnetic susceptibility data for all the samples follow the Curie-Weiss law between 40 and 300 K. The values of the effective magnetic moment μβα are close to those expected for the free R3+ ions. Negative values of the paramagnetic Curie temperature θρ indicate antiferromagnetic interactions. For R = Ho and Tm, the specific heat C(T) data exhibit no anomaly down to 0.4 K, which is ascribed to the nonmagnetic singlet ground states under the crystalline electric fields. On the other hand, for R = Er, C(T) shows peaks at T1 = 1.3 K and T2 = 0.9 K, indicating successive antiferromagnetic transitions. For R = Yb, C(T) shows a lambda-type anomaly at Tm = 1.8 K. The magnetic entropy at Tm is only 30% of Rln2 expected for the ground state doublet, suggesting magnetic fluctuations above Tm.

Anti-CD20 monoclonal antibodies (MoAbs), rituximab (RIT), and obinutuzumab (OBZ) are the central components of immunochemotherapy for B-cell lymphoma (BCL). However, these agents potentially cause B-cell depletion, resulting in the impairment of antibody (Ab) production. During the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) pandemic, the optimal prediction of Ab response against anti-SARS-CoV-2 vaccination is critically important in patients with BCL treated by B-cell depletion therapeutics to prevent coronavirus disease 2019 (COVID-19).  We investigated the effect of using RIT and/or OBZ on the Ab response in 131 patients with various types of BCL who received the second SARS-CoV-2 mRNA vaccine either after, during, or before immunochemotherapy containing B-cell-depleting moiety between June and November 2021 at seven institutes belonging to the Kyoto Clinical Hematology Study Group. The SARS-Cov-2 neutralizing Ab (nAb) was measured from 14 to 207 days after the second vaccination dose using the iFlash3000 automatic analyzer and the iFlash-2019-nCoV Nab kit. Among 86 patients who received the vaccine within 12 months after B-cell depletion therapy, 8 (9.3%) were seropositive. In 30 patients who received the vaccine after 12 months from B-cell depletion therapy, 22 (73%) were seropositive. In 15 patients who were subjected to B-cell depletion therapy after vaccination, 2 (13%) were seropositive. The multivariate analysis indicated that an interval of 12 months between B-cell depletion therapy and the subsequent vaccination was significantly associated with effective Ab production. Receiver operating characteristic curve analysis identified the optimal threshold period after anti-CD20 MoAb treatment, which determines the seropositivity against SARS-CoV-2, to be 342 days. The use of anti-CD20 MoAb within 12 months before vaccination is a critical risk for poor Ab response against anti-SARS-CoV-2 vaccination in patients with BCL.

CePt6Al3 is a rare example of the Ce-based honeycomb lattice compound. Substitution of the isovalent Pt for Pd transforms the ground state from a paramagnetic heavy-fermion state to an antiferromagnetic (AFM) ordered state. To gain insight into the role of magnetic frustration in the honeycomb Kondo lattice, we have measured the magnetization M(B) and electrical resistivity ρ(B) of Ce(Pt1-xPdx)6Al3 (x ≤ 0.3) in pulsed magnetic fields up to 60 T. For the single crystal with x = 0, M(B) for B along the easy c axis exhibits a metamagnetic increase and ρ(B || c) bends at Bm = 28 T. Taking the temperature at a shoulder in the magnetic susceptibility χ(ल) for B ‖ c as Tχm = 17 K, the ratio μBBm/KBT>χm is estimated to be 1.1. This value agrees with those reported for Ce-based paramagnetic heavy-fermion compounds with similar magnitudes of Bm. With increasing x from 0 to 0.3 in polycrystalline samples, the magnitude of M(B = 60 T) at 1.4 K increases from 0.75 to 2.0 μβ/Ce, indicating the recovery of localized 4f moments by the Pd substitution for Pt. Using the data of M(B) and ρ(B) for x = 0.1, 0.2, 0.3, we constructed B-T phase diagrams, which show a trend from a small moment AFM ordered state for x = 0.1 to a large moment AFM ordered state for x = 0.3.

A quantum critical point occurs when different stable phases of matter are in equilibrium at absolute zero temperature. Describing quantum criticality with a theoretical framework that unifies different types of transitions is highly desirable to understand how phenomena such as superconductivity and magnetism interact in correlated electron systems. A study now provides an indication of an underlying universality of quantum criticality, and highlights the role of dimensionality in such a unified theory. How ground states of quantum matter transform between one another reveals deep insights into the mechanisms stabilizing them. Correspondingly, quantum phase transitions are explored in numerous materials classes, with heavy-fermion compounds being among the most prominent ones. Recent studies in an anisotropic heavy-fermion compound have shown that different types of transitions are induced by variations of chemical or external pressure 1 , 2 , 3 , raising the question of the extent to which heavy-fermion quantum criticality is universal. To make progress, it is essential to broaden both the materials basis and the microscopic parameter variety. Here, we identify a cubic heavy-fermion material as exhibiting a field-induced quantum phase transition, and show how the material can be used to explore one extreme of the dimensionality axis. The transition between two different ordered phases is accompanied by an abrupt change of Fermi surface, reminiscent of what happens across the field-induced antiferromagnetic to paramagnetic transition in the anisotropic YbRh 2 Si 2 . This finding leads to a materials-based global phase diagram—a precondition for a unified theoretical description.

Powder neutron diffraction measurements were carried out to investigate the magnetic structure of the antiferromagnet NdRh2Zn20. The magnetic reflections observed for T ≤ 1.0 K are indexed by the propagation vector of k = (1/2, 1/2, 1/2). From the analysis of the intensity of magnetic reflections, a magnetic structure described by the Γ6 representation is proposed. The magnetic moments are parallel to the [112¯] or [1¯10] direction and stacked with a sequence of up-up-down-down along the [111] direction.

For realizing high power generator efficiency based on thermoelectricity, Si, Ge and SiGe nanostructures have attracted attention. In this paper, we have investigated a new approach to fabricate an ultrathin polycrystalline SiGe-on-insulator (pc-SGOI) substrate by a simple process based on Si and Ge deposition followed by thermal diffusion suitable for thermoelectric devices. A 45-nm-thick SGOI layer with a Ge fraction of nearly 0.45 was fabricated, and the Ge fraction was homogeneous in plane over the layer. Its thermal conductivity was 0.87 W mK−1, lower than that of a single-crystalline SGOI layer. This is caused by the enhancement of scattering of phonons at grain boundaries in the pc-SGOI layer.

We measured temperature dependence of electrical resistivity and the specific heat as a function of magnetic field up to 8 T in CeAl2. At the metamagnetic transition around 6 T, the coefficient A (ρ ∞ AT2) and Sommerfeld coefficient reduce by 25 %. Such non drastic reduction implies magnetically insensitive phonon could enhance the A and γ in CeAl2 even in low temperature.

We measured magnetoresistance of the quadrupole ordered system PrV2Al20 with a Γ3 doublet ground state under high-DC magnetic field up to 30 T. The field dependence of the magnetoresistance is strongly different between H [111] and H [110] in spite of the cubic crystal structure. For H [110], we observed a jump with distinct hysteresis between 13 and 16 T and a shoulder structure in the field of 8 T at 23 mK.

We succeeded in growing single crystals of α-YbAl1-xMnxB4 by the substitution of Mn for the Al site in the intermediate-valence rare-earth heavy fermion system α-YbAlB4. We performed specific heat and resistivity measurement on single crystals of α-YbAl1-xMnxB4 (x = 40). In the specific heat measurement on α-YbAl0.60Mn0.40B4, a sharp peak was observed at magnetic transition temperature TM = 9.7(6) K. The resistivity measurements on x = 0.40 also show a semiconductor-like behavior in the entire temperature range from 2 - 300 K. An inclination change was also observed at 10(1) K in resistivity measurement. These results indicate a magnetic order. The magnetic transition temperature is quite high compared to its temperatures observed in the other Yb-based heavy fermion compounds.