Y. Muro

Long-time variation of magnetic structure in CeIr3Si2

CeIr3Si2 shows successive magnetic transitions at TN1=4.1 K and TN2=3.3 K. At T < TN2 it shows three-step metamagnetic transitions below H=1.43 T. In this non-diluted compound a long-time variation of magnetic structure has been detected by means of magnetc susceptibility and time-resolved neutron scattering measurements. When a sample is rapidly cooled below TN2, the magnetic Bragg peaks corresponding to the intermediate temperature phase (TN2 < T < TN1) are observed. The amplitude of these Bragg peaks gradually decreases with time. On the other hand, another group of Bragg peaks corresponding to the low temperature phase (T < TN2) gradually grow with time. The characteristic time for these variations follows the Arrhenius law with an activation energy Ea/kB =4 K. This is the first observation of long-time variation of magnetic structure in non-diluted uniform magnets.

Real-time observation of magnetic structural change in the multistep metamagnet CeIr3Si2

A ternary intermetallic compound CeIr3Si2 shows successive magnetic transitions at TN1=4.1 K and TN2=3.3 K. At T < TN2 it shows three-step metamagnetic transitions below H=1.43 T. In this non-diluted compound a long-time variation of magnetic structure has been detected by means of time-resolved neutron scattering measurements. When a sample is rapidly cooled below TN2, the magnetic Bragg peaks corresponding to the intermediate temperature phase (TN2 < T < TN1) are observed. The amplitude of these Bragg peaks gradually decreases with time. On the other hand, another group of Bragg peaks corresponding to the low temperature phase (T < TN2) gradually grow with time. The characteristic time for these variations follows the Arrhenius law with an activation energy Ea/kB =4 K.

Magnetic properties of phase separated glasses and glass ceramics in Co3O4-TiO2-SiO2 system

The phase separated glass ceramics in Co3O4-TiO2-SiO2 ternary system were prepared by a melt-quenching method and their magnetic properties were investigated. The samples in the xCoO-(48.5 – 0.5x)TiO2-(48.5 – 0.5x)SiO2-3.0Al2O3 (x = 3, 5, 10) consisted of TiO2-rich particles and a SiO2-rich matrix and this phase-separated structure was formed by a nucleation-growth process. This phase-separated glass ceramics showed the magnetic hysteresis loop due to a mixture of ferromagnetic and paramagnetic phases. From the X-ray diffraction measurements, it was confirmed that the samples had the TiO2 rutile phase and amorphous phase without the other crystalline phases. The magnetic susceptibility increased and the coercive force decreased with increasing the amount of Co addition. These results indicated that the prepared samples had the ferromagnetic Co-doped TiO2 rutile phase and the paramagnetic amorphous phase which contains Co divalent ions.

Magnetic Field Dependence of Magnetic Clusters in the Random Magnet Fe65(Ni0:78Mn0:22)35

A neutron scattering study on a concentrated spin-glass alloy Fe65(Ni0:78Mn0:22)35 has been performed under magnetic field. The amplitude of the magnetic diffuse scattering pattern arising from short-range ferromagnetic correlations is markedly reduced by increasing magnetic field. On the other hand, the effect of external field on the diffuse scattering pattern arising from antiferromagnetic short-range correlations is small. These results show that the regions of ferromagnetic and antiferromagnetic shortrange correlations (ferromagnetic and antiferromagnetic clusters) coexist separately in this random magnetic material.

Magnetic and Electric Properties of Phase Separated Glass Ceramics in CoO–TiO 2 –SiO 2 System Prepared by Melt Quenching Process

The developments of high performance magnetic materials are required in various applications such as high sensitive magnetic sensing and hyperthermia in cancer treatment. Recently, Co-doped TiO 2 has been received considerable attention as a candidate for such materials because of their ferromagnetic properties at room temperature. On the other hand, the phase-separated glasses and the derived glass-ceramics having unique micro-nano structure are utilized for various applications. In this study, the phase separated glass-ceramics in CoO-TiO 2 -SiO 2 system with Al 2 O 3 addition were prepared by melt-quenching process. The as-quenched samples consisted of the TiO 2 -rich phase and the SiO 2 -rich one which were formed by a nucleation-growth mechanism of phase separation. From the results of XRD measurements, the samples were found to have a TiO 2 crystalline phase and a SiO 2 -rich glassy phase. The samples showed the magnetic property, which were regarded as a mixture of ferromagnetic and paramagnetic phases. The samples also showed the electric conductivity at room temperature. However, the conductivity of the sample decreased with increase of the Co content, and the temperature dependence of the conductivity of the ferromagnetic samples was different from the other ones. As a result, the Co ions in the phase-separated glass-ceramics in TiO 2 -SiO 2 system were found to affect on both the magnetic and the electric conductive characteristics.

Heavy-fermion behavior in CeRh2SiCeRh2Si

We report on the results of the magnetic susceptibility χ(T)χ(T), electrical resistivity ρ(T)ρ(T) and specific heat C(T)C(T) of CeRh2SiCeRh2Si, which crystallizes in a new BaAl4BaAl4-derivative structure. The Curie–Weiss behavior in χ(T)χ(T) reveals that Ce ions in CeRh2SiCeRh2Si is trivalent. At low temperatures, χ(T)χ(T) shows a broad peak at 1xa0K and a hysteresis below the peak temperature. These observations suggest that CeRh2SiCeRh2Si undergoes a spin-glass transition at Tsg∼1K. On the other hand, heavy-fermion behavior was recognized by two maxima in ρ(T)ρ(T) and a large electronic specific heat coefficient ∼100mJ/molK2. Therefore, CeRh2SiCeRh2Si is a heavy-fermion compound.

Heavy-fermion behavior in CeRh2Si

We report on the results of the magnetic susceptibility χ(T)χ(T), electrical resistivity ρ(T)ρ(T) and specific heat C(T)C(T) of CeRh2SiCeRh2Si, which crystallizes in a new BaAl4BaAl4-derivative structure. The Curie–Weiss behavior in χ(T)χ(T) reveals that Ce ions in CeRh2SiCeRh2Si is trivalent. At low temperatures, χ(T)χ(T) shows a broad peak at 1xa0K and a hysteresis below the peak temperature. These observations suggest that CeRh2SiCeRh2Si undergoes a spin-glass transition at Tsg∼1K. On the other hand, heavy-fermion behavior was recognized by two maxima in ρ(T)ρ(T) and a large electronic specific heat coefficient ∼100mJ/molK2. Therefore, CeRh2SiCeRh2Si is a heavy-fermion compound.

Heavy-fermion behavior in

We report on the results of the magnetic susceptibility χ(T)χ(T), electrical resistivity ρ(T)ρ(T) and specific heat C(T)C(T) of CeRh2SiCeRh2Si, which crystallizes in a new BaAl4BaAl4-derivative structure. The Curie–Weiss behavior in χ(T)χ(T) reveals that Ce ions in CeRh2SiCeRh2Si is trivalent. At low temperatures, χ(T)χ(T) shows a broad peak at 1xa0K and a hysteresis below the peak temperature. These observations suggest that CeRh2SiCeRh2Si undergoes a spin-glass transition at Tsg∼1K. On the other hand, heavy-fermion behavior was recognized by two maxima in ρ(T)ρ(T) and a large electronic specific heat coefficient ∼100mJ/molK2. Therefore, CeRh2SiCeRh2Si is a heavy-fermion compound.