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Ítem Acceso Abierto Competition between ferromagnetism and frustrated antiferromagnetism in quasi 2D Ce 2.15 (Pd1_xAgx) 1.95In0.9 alloys(IOP Publishing, 2016-09-16) Sereni, J.G; Giovannini, M.; Gomez Berisso, M.; Gastaldo, F.; Gerencia Física. Departamento Materia Condensada. División Bajas TemperaturasLow temperature thermal and magnetic measurements performed on ferro-magneticl (FM) alloys of composition Ce2.15(Pd1−xAgx)1.95In0.9 are presented. Pd substitution by Ag depresses TC(X) from 4.1 K down to 1.1 K for x = 0.5, which is related to the increase of band electrons, with a critical concentration extrapolated to xcr≈ 0.6. The TC(x) decrease is accompanied by a weakening of the magnetization of the FM phase. At high temperature (T > 30 K) the inverse magnetic susceptibility reveals the presence of robust magnetic moments (2.56 ≥ μeff≥2.4μB), whereas the low value of the Curie–Weiss temperature ɵp≈ -10K excludes any relevant effect from Kondo screening. The specific heat jump at TC(X) decreases accordingly, while an anomaly emerges at a fixed temperature T*≈1K K. This unexpected anomaly does not show any associated sign of magnetism checked by AC-susceptibility measurements. Since the total magnetic entropy (evaluated around T=TC(X=0)) practically does not change with Ag concentration, the transference of degrees of freedom from the FM component to the non-magnetic T* anomaly is deduced. The origin of this anomaly is attributed to an arising magnetic frustration of the ground state and the consequent entropy bottleneck produced by the divergent increasing of density of excitations at low temperature.Ítem Acceso Abierto Experimental Heat Capacity of Pure Liquid He3(American Physical Society, 1969-09-00) Mota, A.C.; Platzeck, R.P.; Rapp, R.; Wheatley, J.C.; Gerencia Física. Departamento Materia Condensada. División Bajas TemperaturasMeasurements of the heat capacity of pure He3 at 0.24 atm obtained by a differencing method are presented for the temperature range from 20-150 m°K. The temperature scale T∗ used is that valid for powdered cerium magnesium nitrate in the form of a right circular cylinder with diameter equal to height. There is excellent agreement between the present and earlier measurements. Considering all low-pressure difference data we find that from 6-125 m°K the ratio of heat capacity to magnetic temperature decreases linearly with increasing temperature. The relationship of the measurements to the temperature scale and to theories of spin fluctuations in He3 is also discussed.Ítem Acceso Abierto Low-Temperature Specific Heats of the beta and zeta Phases in Equiatomic AgZn(American Physical Society, 1970-09-15) Abriata, J. P.; Bressan, O. J.; Luengo, C. A.; Thoulouze, D.; Gerencia Física. Departamento Materia Condensada. División Bajas TemperaturasHeat-capacity measurements between 1.3 and 4.2°K have been made on equiatomic AgZn in both the β′ and ζ0 phases. Significant differences were found in the Debye temperature and the electronic specific-heat coefficient, the latter data being discussed in terms of Fermi-surface-Brillouin-zone interactions. Furthermore, it is concluded that β′ is the stable phase at 0°K, and that in this particular alloy, vibrational properties are of major importance in controlling phase stability near 0°K.Ítem Acceso Abierto Magnetic and thermal properties of Ce2Pd2Sn(Elsevier, 2008-03-00) Braghta, A.; Schmerber, G.; Derory, A.; Sereni, J.G.; Kappler, J.P.; Gerencia Física. Departamento Materia Condensada. División Bajas TemperaturasX-ray diffraction, susceptibility and specific heat studies on ternary Ce2Pd2Sn intermetallic compound and on its isostructural non-magnetic compound La2Pd2Sn are reported. On Ce2Pd2Sn in absence of magnetic field, we confirm the existence of two magnetic transitions at TN=4.8 K (antiferromagnetic transition) and TC=2.2 K (ferromagnetic transition) and the specific heat results, measured down to 0.5 K, allow to recognize the transition at 2.2 K as a first-order transition. A description based on molecular field calculations for the S=1/2 resonant level model leads to a characteristic Kondo TK of about 3 K.Ítem Acceso Abierto Magnetization and specific heat of La doped Sr2FeMoO6(Elsevier, 2004-05-00) Tovar, M.; Sereni, J.G.; Pedrazzini, P.; Caneiro, A.; Prado, F.; Butera, A.; Causa, M.T.; Gerencia Física. Departamento Materia Condensada. División Bajas TemperaturasWe present high-temperature magnetization and low-temperature specific heat measurements performed on the electron doped double perovskite Sr1.7La0.3FeMoO6. We have obtained the electronic contribution to Cp, γ=11.5(5) mJ/mol K2. The electronic susceptibility, derived from the magnetic measurements in the paramagnetic regime (T>Tc=390 K), was χe0=(4.9±1.5)×10−4 emu/mol. Antiferromagnetic coupling between localized and itinerant moments was inferred from the data, with a coupling constant λ=−(475±50) mol/emu, that results in a ferromagnetic-like Curie–Weiss susceptibility with Θ=390(5) K. These results are compared with those obtained for the undoped material.Ítem Acceso Abierto Specific heat, magnetic susceptibility and electrical resistivity measurements on LaNiO3(Elsevier, 1993-02-19) Sanchez, R.D.; Causa, M.T.; Sereni, J.G.; Vallet-Regi, M.; Sayaguez, M.J.; Gonzalez-Calbet, J.M.; Gerencia Física. Departamento Materia Condensada. División Bajas TemperaturasMeasurements of specific heat, magnetic susceptibility and electrical resistivity on LaNiO3 are reported. No evidence of magnetic ordering or metal-insulator transitions is found. From the measured electronic specific heat parameter γ and the Pauli susceptibility χP, a Stoner enhancement parameter is derived. Comparison with band structure calculations performed by other workers is also made.