J.M. Machado da Silva

A pull-in based test mechanism for device diagnostic and process characterization

A test technique for capacitive MEMS accelerometers and electrostatic microactuators, based on the measurement of pull-in voltages and resonance frequency, is described. Using this combination of measurements, one can estimate process-induced variations in the device layout dimensions as well as deviations from nominal value in material properties, which can be used either for testing or device diagnostics purposes. Measurements performed on fabricated devices confirm that the 250 nm overetch observed on SEM images can be correctly estimated using the proposed technique.

Low temperature specific heat investigation of the mixed-valence regime in the laves system Ce(Co1−xNix)2

Abstract Heat capacity measurements of the system Ce(Co 1−xNi x ) 2 are consistent with a significant change in the valency of cerium above x ≈ 0.67. The composition dependence of γ is understood within Fermi liquid theory.

The heat capacity of LaPd3 and PrPd3 at low temperature

Abstract Values of γ=0.33±0.01 mJ/K2·g atom and θD=176±1 K were found for LaPd3. PrPd3 shows magnetic ordering below 0.6 K and a Schottky anomaly whose maximum lies around 1.8 K. The crystalline field at the Pr3+ site creates a Γ3 (doublet) excited state lying 4 K above the Γ5 (triplet) ground state.

Heat capacity and magnetic interactions in copper formate dihydrate

Abstract The heat capacity of copper formate dihydrate was measured. The characteristic feature of the heat capacity curve was well understood by assuming the alternating piling up of ferromagnetic (100) layers and paramagnetic (200) layers and a weak interlayer interaction. By analysis of the results, the intra and interlayer interactions JAA and JAB were estimated as 1.5 K and 0.37 K, respectively.

Submillimeter wave ESR and magnetization measurements of CexGd1 − xCo2

Abstract Submillimeter wave ESR measurements of MgCu2-type cubic Laves phase material CexGd1 − xCo2 (0 ⩽ x ⩽ 1) has been performed at 4.2 K in the frequency region from 90 to 240 GHz using pulsed magnetic fields. Due to the metallic properties of the samples, the strip-line technique was used. A concentration (x) dependence of the shift of the resonance was observed. The results are discussed in connection with those of the magnetization measurements.

ESR characterization of the spin-glass AgMn

Abstract ESR measurements on six samples of Ag Mn (c = 2.13, 4.96, 6.35, 9.54, 13.02 and 19.29 at%) have been interpreted by means of the model of Schultz et al.; our experimental results are consistent with the view that the frequency of resonance is a linear function of the resonant field. The uniaxial anisotropy constant depends linearly on the temperature: K(T)/K(0) = 1 − βT/Tg with β = 0.78. The unidirectional anisotropy is observed below about 0.4 Tg for a field cooled specimen (c = 6.35 at%).

Dzyaloshinskii–Moriya nature of ferroelectric ordering in magnetoelectric Gd1−xYxMnO3 system

Abstract The phase diagram of Gd 1− x Y x MnO 3 , 0≤ x ≤0.4, is presented and the role of the driving mechanisms in stabilizing both magnetic and ferroelectric orderings is discussed in the framework of the Dzyaloshinskii–Moriya model. The ( x , T ) phase diagram reflects the effect of lattice distortions induced by the substitution of Gd 3+ ion by smaller Y 3+ ions, which gradually unbalances the antiferromagnetic against the ferromagnetic exchange interactions, enabling the emergence of ferroelectricity for higher concentrations of yttrium.

Electrical resistivity of Gd4(Co1−xCux)3 compounds

In order to study the effects caused by substituting Co for Cu on the electronic and transport properties of Gd4(Co1−xCux)3 compounds with x=0.05, 0.1, 0.2, and 0.3, electrical resistivity [ρ(T)] measurements were performed in the temperature range 12–300K. The paramagnetic-ferrimagnetic and spin-reorientation transitions are marked by clear anomalies in dρ∕dT. For x=0.2, however, the onset of ferrimagnetic order at TC produces just a comparatively small peak in dρ∕dT. This fact is compatible with a hypothetical mixed ferrimagnetic phase exhibiting partial disorder of the magnetic moments, as suggested by magnetic measurements [T. M. Seixas, J. M. Machado da Silva, H. F. Braun, and G. Eska (unpublished)]. The spin disorder resistivity shows a pronounced decrease with increasing x that can be attributed to the observed reduction of the magnetic moment of Co atoms. This stresses the important role played by 3d-band electrons in both magnetic state and in the strong s‐d electron scattering. Magnon-induced el...

Mixed-signal BIST using correlation and reconfigurable hardware (poster paper)

ReducingtheareaoverheadrequiredbyBISTstructures canbeachievedby reconfiguringexistinghardware to perform test related control and processingfunctions. This work showshow the resour ces required for theseoperations can be implementedin-circuit, taking advantageof programmablelogic availablein thesystem.Structural and functional testsare performedusingcorrelation to obtain and cross-corr elation signatures, and to measure gain,phase,andtotal harmonicdistortion.

Mixed-signal BIST using correlation and reconfigurable hardware

Reducing the area overhead required by BIST structures can be achieved by reconfiguring existing hardware to perform test related control and processing functions. This work shows how the resources required for these operations can be implemented in-circuit, taking advantage of programmable logic available in the system. Structural and functional tests are performed using correlation to obtain i/sub DD/ and /spl nu//sub OUT/ cross-correlation signatures, and to measure gain, phase, and total harmonic distortion.