arXiv subjects

C. Thessieu

Publications and source records attributed to C. Thessieu.

5 recordsLinked to original sources

arXiv2001

Pressure-Temperature Phase Diagram of Antiferromagnetism and Superconductivity in CeRhIn5 and CeIn3 : In-NQR Study under Pressure

We report the novel pressure($P$) - temperature($T$) phase diagram of antiferromagnetism and superconductivity in CeRhIn$_5$ and CeIn$_3$ revealed by the $^{115}$In nuclear-spin-lattice-relaxation ($T_1$) measurement. In the itinerant magnet CeRhIn$_5$, we found that the Néel temperature $T_N$ is reduced at $P \geq$ 1.23 GPa with an emergent pseudogap behavior. In CeIn$_3$, the localized magnetic character is robust against the application of pressure up to $P \sim$ 1.9 GPa, beyond which the system evolves into an itinerant regime in which the resistive superconducting phase emerges. We discuss the relationship between the phase diagram and the magnetic fluctuations.

cond-mat.str-el↗

arXiv2000

Exotic Superconducting Phase in CeCu2Si2 Close to Antiferromagnetism : A Cu-NQR Study under Hydrostatic Pressure

We report Cu nuclear-quadrupole-resonance results under pressure on a homogeneous CeCu2Si2 (Tc = 0.65 K) that revealed critical magnetic fluctuations at the border to an antiferromagnetic phase. This exotic superconducting phase evolves into the typical heavy-fermion superconducting phase at minute pressures exceeding Pc ~ 0.2 GPa. The nuclear spin-lattice relaxation data in a pressure range 0.85 - 2.58 GPa are shown to be accountable by the SCR theory based on the nearly antiferromagnetic Fermi-liquid model. In 0 < P < Pc ~ 0.2 GPa, by contrast, we conclude that the exotic superconducting phase manifests itself under the unconventional normal state where antiferromagnetic waves propagate over a long range without any trace of antiferromagnetic order and thereby the heavy-fermion state breaks up.

cond-mat.str-el↗

arXiv1998

NMR Study of MnSi under Pressure

The magnetic phase diagram $T_c(P)$ of the weak itinerant helimagnetic compound MnSi is reviewed upon a Nuclear Magnetic Resonance (NMR) experiment. We present a systematic study on the evolution of the NMR spin echo signal at $T=1.4$ K of the non-magnetic silicone sites, $^{29}$Si, up to 17.8 kbar. The pressure effect is interpreted as a weak variation of the local electronic spin polarization and the coexistence of magnetic and non magnetic Mn atoms under pressure. From the volume dependence of $f_0$ ($P$), we show notably that a local magnetic order remains above the critical pressure of $P_c=14.8$ kbar.

cond-mat.str-el↗

arXiv1998

Magnetization under High Pressure in MnSi

The magnetization M(H) has been measured in the weakly helimagnetic itinerant compound MnSi under high pressure up to 10.2 kbar and high magnetic field up to 9 Tesla. We interpret the simultaneous decrease under pressure of the saturated magnetization, $p_s$, and the Curie temperature, $% T_c$ in the frame of the self-consistent renormalization theory (SCR) of spin fluctuations. From the analysis of the so-called Arrot-plot ($H/p [ H,T ] $ versus $p^2[ H,T ] $) and the respective volume dependence of $p_s$ and $T_c$, we estimate the evolution of the characteristic spin fluctuation temperatures, $T_0$ and $T_A$ when the system approaches its critical pressure, $P_c$=15 kbar, corresponding to the disappearance of the long range magnetic order at T=0.

cond-mat.str-el↗

arXiv1998

Pressure Effect on the Spin Fluctuations in YMn$_2$ --Mn NQR Study--

We report the NQR study on the pressure-induced paramagnetic state in the antiferromagnetic (AF) intermetallic compound YMn$_2$ with the Néel temperature T_N=100 K at ambient pressure. From the $T$ variation of the nuclear spin-lattice relaxation rate, $^{55}(1/T_1)$ of $^{55}$Mn above the critical pressure of 4 kbar, the spin fluctuation feature is found to change below a temperature $T_{sf}$. At higher temperature than $T_{sf}$, the nuclear relaxation behavior is well described in terms of the self-consistent renomalized (SCR) spin fluctuation theory for nearly AF metals, whereas below $T_{sf}$ a deviation is significant and $1/T_1T$ exhibits a weak $T$ variation. It is pointed out that $T_{sf}$ coincides with the temperature below which a $T^{2}$ law in electrical resistivity is valid as expected for a Fermi liquid ground state. We proposed that these features are understood from the standpoint that the development of AF spin fluctuation remains in short-range associated with the singlet formation among Mn spins in each tetrahedron as suggested by the inelastic neutron experiments on $Y_{1-x}Sc_xMn_2$.

cond-mat.str-el↗