Investigation of metallic/oxide interfaces in Pt/Co/AlOx trilayers by hard x-ray reflectivity

International audienceX-ray reflectivity (XRR) is used to determine the oxidation front at the nanometer scale in sputtered perpendicular semi tunnel junctions, as the form Pt/Co/AlOx, by varying the oxidation time tOx of the capping layer. From XRR simulations, we show that the nature of the stack is gradually defined according to the value of tOx. For low tOx values (<40 s), a simple Pt/Co/Al/AlOx multilayer is appearing whereas a Pt/Co/CoO/AlOx architecture takes place for higher tOx. The oxygen-induced magnetic properties obtained by extraordinary Hall effects measurements are explained by the structural results. The increase of Co-O bondings with tOx is at the origin of the appearing of the perpendicular magnetic anisotropy (PMA)

A simple and accurate relative alternative magnetic susceptibility measurement technique

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A new differential thermal analysis setup for measuring high pressure phase transitions

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Calorimetric investigation of the magnetocaloric effect in Ni45Co5Mn37.5In12.5

International audienceA calorimetric investigation of a Ni45Co5Mn37.5In12.5 single crystal has been carried out by combining differential scanning calorimetry (DSC) and heat capacity (C) measurements. The martensitic transition showing a first-order character spread over a wide temperature range, a specific measuring technique of C(T) has been developed. This method—based on a time-resolved analysis of successive heating pulses—was found to yield an entropy change at the transition (ΔStr) that is very close to that derived from DSC. To investigate the magnetocaloric effect, both the isothermal entropy change ΔST and the adiabatic temperature change ΔTad were derived from heat capacity curves recorded in a series of magnetic fields up to 7 T. The maximum values of ΔST(T, B) were observed to be in accordance with those determined from the Maxwell equation. Furthermore, maximum values of ΔTad(T, B) resulting from the application of 2 T, 5 T and 7 T were found to be equal to −2.3 K, −6.1 K and −9.4 K, respectively

Differences and Similarities between Lanthanum and Rare-Earth Iodate Anhydrous Polymorphs: Structures, Thermal Behaviors, and Luminescent Properties

International audienceThe Ln(IO)(HIO) (y = 1 or 1.33) compounds are isostructural with the La(IO)(HIO) phases, but thermal studies reveal different behaviors. On the one hand, the partial thermal decompositions of these lanthanide compounds lead to the Ln(IO) formulation, with a room temperature structure different from the β-La(IO) obtained from La(IO)(HIO). On the other hand, the partial thermal decompositions of the LaLn(IO)(HIO) compounds prepared with lanthanides ions (Ce, Pr, Nd, Sm, Eu, Gd, and Yb) lead to acentric β-LaLn(IO). As for β-La(IO), reversible structural transitions from β-LaLn(IO) to centrosymmetric γ-LaLn(IO) are observed. Differential scanning calorimetry analyses of LaLn(IO) solid solutions show that the transition temperatures vary with the lanthanide concentration in the solid solution. A transition is observed only up to a certain fraction of lanthanide-ion substitution; this substitution limit decreases with the cationic radius of the lanthanide ion. Finally, the β-LaNd(IO) and β-LaYb(IO) phases are investigated by luminescence spectroscopy

Calorimetric investigation of the magnetocaloric effect in Ni45Co5Mn37.5In12.5

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Influence of benzene on the Ni3Fe nanocrystalline compound formation by wet mechanical alloying: An investigation combining DSC, X-ray diffraction, mass and IR spectrometries

International audienceNanocrystalline Ni3Fe powders were obtained via wet mechanical alloying using benzene as surfactant. The differential scanning calorimetry (DSC) measurements showed the presence of an exothermic peak which does not correspond to any phase transformation or phase formation as was proved by X-ray diffraction measurements. The exothermic peak was observed neither for the dry milled samples nor for the wet milled and subsequently annealed powders at 350 degrees C for 4 h. The infra-red (IR) spectra registered for the wet milled samples showed a series of vibration bands corresponding to C6H6 and also to a series of fragments resulting from benzene decomposition. The results obtained by IR investigation were confirmed by thermogravimetry and mass spectrometry (TG + MS) investigations. The main fragments resulting from the benzene decomposition on the surface of the nanocrystalline Ni3Fe powders are: CO2, CO and C. The evolution of the particle size distribution versus the milling time has been determined for the wet mechanical milling process of nanocrystalline Ni3Fe powders. The DSC analysis reveals a displacement of the exothermic peak onset towards lower temperatures and an increase of the surface of this peak attributed to the changes in the particles specific surface and to the quantity of benzene added in the milling experiments