arXiv subjects

Masatsugu Suzuki

Publications and source records attributed to Masatsugu Suzuki.

24 records · Page 2Linked to original sources

arXiv2003

Magnetic phase diagram of three-dimensional diluted Ising antiferromagnet Ni$_{0.8}$Mg$_{0.2}$(OH)$_{2}$

$H$-$T$ diagram of 3D diluted Ising antiferromagnet Ni$_{c}$Mg$_{1-c}$(OH)$_{2}$ with $c$ = 0.8 has been determined from measurements of SQUID DC magnetization and AC magnetic susceptibility. At $H$ = 0, this compound undergoes two magnetic phase transitions: an antiferromagnetic (AF) transition at the Néel temperature $T_{N}$ (= 20.7 K) and a reentrant spin glass (RSG) transition at $T_{RSG}$ ($\approx$ 6 K). The $H$-$T$ diagram consists of the RSG, spin glass (SG), and AF phases. These phases meet a multicritical point $P_{m}$ ($H_{m}$ = 42 kOe, $T_{m}$ = 5.6 K). The irreversibility of susceptibility defined by $δ$ (= $χ_{FC} - χ_{ZFC}$) shows a negative local minimum for 10 $\leq H \leq$ 35 kOe, suggesting the existence of possible glassy phase in the AF phase. A broad peak in $δ$ and $χ^{\prime \prime}$ at $H \geq$ 20 kOe for $T_{N}(c=0.8,H) \leq T \leq T_{N}(c=1,H=0)$ (= 26.4 K) suggests the existence of the Griffiths phase.

cond-mat.dis-nn↗

arXiv2003

H-T phase diagram and the nature of Vortex-glass phase in a quasi two-dimensional superconductor: Sn metal layer sandwiched between graphene sheets

The magnetic properties of a quasi two-dimensional superconductor, Sn-metal graphite (MG), are studied using DC and AC magnetic susceptibility. Sn-MG has a unique layered structure where Sn metal layer is sandwiched between adjacent graphene sheets. This compound undergoes a superconducting transition at $T_{c}$ = 3.75 K at $H$ = 0. The $H$-$T$ diagram of Sn-MG is similar to that of a quasi two-dimensional superconductors. The phase boundaries of vortex liquid, vortex glass, and vortex lattice phase merge into a multicritical point located at $T^{*}$ = 3.4 K and $H^{*}$ = 40 Oe. There are two irreversibility lines denoted by $H_{gl}$ (de Almeida-Thouless type) and $H_{gl^{\prime}}$ (Gabay-Toulouse type), intersecting at $T_{0}^{\prime}$= 2.5 K and $H_{0}^{\prime}$ = 160 Oe. The nature of slow dynamic and nonlinearity of the vortex glass phase is studied.

cond-mat.supr-con↗

arXiv2003

Magnetic-field induced superconductor-metal-insulator transitions in bismuth metal-graphite

Bismuth-metal graphite (MG) has a unique layered structure where Bi nanoparticles are encapsulated between adjacent sheets of nanographites. The superconductivity below $T_{c}$ (= 2.48 K) is due to Bi nanoparticles. The Curie-like susceptibility below 30 K is due to conduction electrons localized near zigzag edges of nanographites. A magnetic-field induced transition from metallic to semiconductor-like phase is observed in the in-plane resistivity $ρ_{a}$ around $H_{c}$ ($\approx$ 25 kOe) for both $H$$\perp$$c$ and $H$$\parallel$$c$ ($c$: c axis). A negative magnetoresistance in $ρ_{a}$ for $H$$\perp$$c$ (0$ $ 40 kOe) suggest the occurrence of two-dimensional weak localization effect.

cond-mat.supr-con↗

arXiv2003

Superconductivity and spin-glass like behavior in system with Pd sheet sandwiched between graphene sheets

Pd-metal graphite (Pd-MG) has a layered structure, where each Pd sheet is sandwiched between adjacent graphene sheets. DC magnetization and AC magnetic susceptibility of Pd-MG have been measured using a SQUID magnetometer. Pd-MG undergoes a superconducting transition at $T_{c}$ ($= 3.63 \pm 0.04$ K). The superconductivity occurs in Pd sheets. The relaxation of $M_{ZFC}$ (aging), which is common to spin glass systems, is also observed below $T_{c}$. The relaxation rate $S(t)$ shows a peak at a characteristic time $t_{cr}$, which is longer than a wait time $t_{w}$. The irreversibility between $χ_{ZFC}$ and $χ_{FC}$ occurs well above $T_{c}$. The susceptibility $χ_{FC}$ obeys a Curie-Weiss behavior with a negative Curie-Weiss temperature ($-13.1 \leq Θ\leq -5.4$ K). The growth of antiferromagnetic order is limited by the disordered nature of nanographites, forming spin glass-like behavior at low temperatures in graphene sheets.

cond-mat.supr-con↗

arXiv2003

Dynamic scaling and aging phenomena in short-range Ising spin glass: Cu$_{0.5}$Co$_{0.5}$Cl$_{2}$-FeCl$_{3}$ graphite bi-intercalation compound

Static and dynamic behavior of short-range Ising-spin glass Cu$_{0.5}$Co$_{0.5}$Cl$_{2}$-FeCl$_{3}$ graphite bi-intercalation compounds (GBIC) has been studied with SQUID DC and AC magnetic susceptibility. The $T$ dependence of the zero-field relaxation time $τ$ above a spin-freezing temperature $T_{g}$ (= 3.92 $\pm$ 0.11 K) is well described by critical slowing down. The absorption $χ^{\prime\prime}$ below $T_{g}$ decreases with increasing angular frequency $ω$, which is in contrast to the case of 3D Ising spin glass. The dynamic freezing temperature $T_{f}(H,ω)$ at which d$M_{FC}(T,H)/$d$H=χ^{\prime}(T,H=0,ω)$, is determined as a function of frequency (0.01 Hz $\leq ω/2π\leq$ 1 kHz) and magnetic field (0 $\leq H \leq$ 5 kOe). The dynamic scaling analysis of the relaxation time $τ(T,H)$ defined as $τ= 1/ω$ at $T = T_{f}(H,ω)$ suggests the absence of SG phase in the presence of $H$ (at least above 100 Oe). Dynamic scaling analysis of $χ^{\prime \prime}(T, ω)$ and $τ(T,H)$ near $T_{g}$ leads to the critical exponents ($β$ = 0.36 $\pm$ 0.03, $γ$ = 3.5 $\pm$ 0.4, $ν$ = 1.4 $\pm$ 0.2, $z$ = 6.6 $\pm$ 1.2, $ψ$ = 0.24 $\pm$ 0.02, and $θ$ = 0.13 $\pm$ 0.02). The aging phenomenon is studied through the absorption $χ^{\prime \prime}(ω, t)$ below $T_{g}$. It obeys a $(ωt)^{-b^{\prime \prime}}$ power-law decay with an exponent $b^{\prime \prime}\approx 0.15 - 0.2$. The rejuvenation effect is also observed under sufficiently large (temperature and magnetic-field) perturbations.

cond-mat.dis-nn↗

arXiv2003

Nonlinear magnetic susceptibility and aging phenomena in reentrant ferromagnet: Cu$_{0.2}$Co$_{0.8}$Cl$_{2}$-FeCl$_{3}$ graphite bi-intercalation compound

Linear and nonlinear dynamic properties of a reentrant ferromagnet Cu$_{0.2}$Co$_{0.8}$Cl$_{2}$-FeCl$_{3}$ graphite bi-intercalation compound are studied using AC and DC magnetic susceptibility. This compound undergoes successive phase transitions at the transition temperatures $T_{h}$ (= 16 K), $T_{c}$ (= 9.7 K), and $T_{RSG}$ (= 3.5 K). The static and dynamic behaviors of the reentrant spin glass phase below $T_{RSG}$ are characterized by those of normal spin glass phase with critical exponent $β$ = 0.57 $\pm$ 0.10, a dynamic critical exponent $x$ = 8.5 $\pm$ 1.8, and an exponent $p$ (= 1.55 $\pm$ 0.13) for the de Almeida -Thouless line. A prominent nonlinear susceptibility is observed between $T_{RSG}$ and $T_{c}$ and around $T_{h}$, suggesting a chaotic nature of the ferromagnetic phase ($T_{RSG} \leq T \leq T_{c}$) and the helical spin ordered phase ($T_{c} \leq T \leq T_{h}$). The aging phenomena are observed both in the RSG and FM phases, with the same qualitative features as in normal spin glasses. The aging of zero-field cooled magnetization indicates a drastic change of relaxation mechanism below and above $T_{RSG}$. The time dependence of the absorption $χ^{\prime \prime}$ is described by a power law form ($\approx t^{-b^{\prime \prime}}$) in the ferromagnetic phase, where $b^{\prime \prime} \approx 0.074 \pm 0.016$ at $f$ = 0.05 Hz and $T$ = 7 K. No $ωt$-scaling law for $χ^{\prime \prime}$ [$\approx (ωt)^{-b^{\prime \prime}}$] is observed.

cond-mat.dis-nn↗