RESUMO
We report a large tunneling anisotropic magnetoresistance (TAMR) in (Ga,Mn)As lateral nanoconstrictions. Unlike previously reported tunneling magnetoresistance effects in nanocontacts, the TAMR does not require noncollinear magnetization on either side of the constriction. The nature of the effect is established by a direct comparison of its phenomenology with that of normal anisotropic magnetoresistance (AMR) measured in the same lateral geometry. The direct link we establish between the TAMR and AMR indicates that TAMR may be observable in other materials showing room temperature AMR and demonstrates that the physics of nanoconstriction magnetoresistive devices can be much richer than previously thought.
RESUMO
Two kinds of chitosan-based hydrogels, a crosslinked chitosan reference gel and a chitosan-poly(ethylene oxide) semi-interpenetrating network (semi-IPN), with potential pH-sensitive swelling and drug delivery properties are characterized. Swelling studies were performed on the two kinds of hydrogels by differential scanning calorimetry (DSC) at pH 1.2 and by the gravimetric method at pH 1.2 and pH 7.2. Both methods lead to similar results. If pH-dependent swelling properties were observed with both hydrogels, they were however improved for the semi-IPN. The amount of bound water in the xerogels could be determined from DSC measurements and a thermogravimetric analysis. The results obtained by both techniques were in good agreement and indicated that the semi-IPN contained more bound water than the reference gel probably due to the presence of the hydrophilic poly(ethylene oxide) chains. Young modulus of the swollen hydrogels was determined by indentation analysis. The semi-IPN displayed improved mechanical properties compared to the reference gel.
