arXiv subjects

F. Gastaldo

Publications and source records attributed to F. Gastaldo.

4 recordsLinked to original sources

arXiv2020

Pressure-Induced Antiferromagnetic Dome in the Heavy-Fermion $Yb_2Pd_2In_{1-x}Sn_x$ System

In the heavy-fermion system $Yb_2Pd_2In_{1-x}Sn_x$, the interplay of crystal-field splitting, Kondo effect, and Ruderman-Kittel-Kasuya-Yosida interactions leads to complex chemical-, pressure-, and magnetic-field phase diagrams, still to be explored in full detail. By using a series of techniques, we show that even modest changes of parameters other than temperature are sufficient to induce multiple quantum-critical transitions in this highly susceptible heavy-fermion family. In particular, we show that, above $\sim 10$ kbar, hydrostatic pressure not only induces an antiferromagnetic phase at low temperature, but it likely leads to a reorientation of the Yb magnetic moments and/or the competition among different antiferromagnetic configurations.

cond-mat.str-el↗

arXiv2019

Suppression of Shastry-Sutherland phase driven by electronic concentration reduction in magnetically frustrated Ce$_2$Pd$_2$Sn$_{1-y}$In$_y$ alloys

Shastry-Sutherland lattice was observed as alternative ground state in Rare Earth intermetallic with Mo$_2$B$_2$Fe and U$_2$Pt$_2$Sn anisotropic structures where magnetic frustration is favored. In the case of Ce$_2$Pd$_2$Sn, it was shown that such phase can be suppressed by the application of magnetic field and, in this work, its stability is studied as a function of the electronic concentration by doping the Sn(4+) lattice with In(3+) atoms. Magnetic and specific heat measurements show that around 50\% substitution the Shastry Sutherland lattice vanishes in a critical point. This result confirms the strong dependence of that phase on the electron density because a recent investigation on the Pd rich solid solution Ce$_{2+ε}$Pd$_{2-ε}$In$_{1-x}$Sn$_x$ (with $ε< 0$) demonstrates that atomic disorder dominates the phase diagram at intermediate Sn/In concentration inhibiting magnetic frustration effects. In the alloys investigated in this work, the $ε>0$ character stabilizes the ferromagnetic ground state all along the concentration, allowing the Shastry Sutherland lattice formation on the Sn rich side.

cond-mat.str-el↗

arXiv2018

YbPd$_2$In: a promising candidate to strong entropy accumulation at very low temperature

We report on synthesis, crystal structure, magnetic, thermodynamic and transport properties of the new compound YbPd$_2$In, crystallizing as a Heusler structure type. A trivalent state of the rare earth was determined by fitting the magnetic susceptibility with a Curie-Weiss law. This compound is characterized by showing very weak magnetic interactions and a negligible Kondo effect. A specific heat jump was observed at $T\approx 250$ mK, followed at higher temperature by a power law decrease of $C_P(T)/T$. The resulting large electronic entropy increase at very low temperature is rapidly shifted to higher temperature by the application of magnetic field. This magnetocaloric effect places YbPd$_2$In as a very good candidate for adiabatic demagnetization cooling processes.

cond-mat.str-el↗

arXiv2015

Emerging frustration effects in ferromagnetic Ce_2[Pd_{1-x}Ag_x]_2In alloys

Magnetic and thermal properties of Ferromagnetic (FM) Ce_{2.15}(Pd_{1-x}Ag_x)_{1.95}In_{0.9} alloys were studied in order to determine the Quantum Critical Point (QCP) at T_C => 0. The increase of band electrons produced by Pd/Ag substitution depresses T_C(x) from 4.1K down to T_C(x=0.5)=1.1K, with a QCP extrapolated to x_{QCP}~ 0.6. Magnetic susceptibility from T>30K indicates an effective moment slightly decreasing from μ_{eff}=2.56μ_B to 2.4μ_B at x=0.5. These values and the paramagnetic temperature θ_P~ -10K exclude significant Kondo screening effects. The T_C(x) reduction is accompanied by a weakening of the FM magnetization and the emergence of a specific heat C_m(T) anomaly at T*~ 1K, without signs of magnetism detected from AC-susceptibility. The magnetic entropy collected around 4K (i.e. the T_C of the x=0 sample) practically does not change with Ag concentration: S_m(4K)~ 0.8 Rln2, suggesting a progressive transfer of FM degrees of freedom to the non-magnetic (NM) component. No antecedent was found concerning any NM anomaly emerging from a FM system at such temperature. The origin of this anomaly is attributed to an 'entropy bottleneck' originated in the nearly divergent power law dependence for T>T*.

cond-mat.str-el↗