Magnetoelastic properties of nickel thin films

Abstract

The deflection of bimorphs consisting of thin films of nickel on silicon substrates has been accurately measured as a function of applied in-plane magnetic field, using an optical method. Striking differences in the magnetoelastic behavior are observed for these systems compared with bulk nickel, mainly due to the anisotropic behavior of silicon substrates and to large in plane tensile stresses in nickel films, which favor an easy magnetization axis perpendicular to the film plane: Deflections measured with the magnetic field parallel and perpendicular to the length of the bimorph exhibit the same sign, and the ‘‘parallel deflection’’ is enhanced by a factor 1.3. These are the first experiments demonstrating the validity of a formula recently derived for predicting the deflection of magnetostrictive bimorphs.

Three terminal capacitance technique for magnetostriction and thermal expansion measurements

“…23 Observed longitudinal and transversal stresses in Ni/Si(111) cantilever exhibit a positive sign in both cases. That agrees well with the previous room temperature data 24 thus confirming the reliability of our experiment. The measurements were then performed on La 0.7 Sr 0.3 CoO 3 film deposited onto SAT0.7CAT0.1LA0.2 twins free (001) oriented substrate(SAT-SrAl 0.5 Ta 0.5 O 3 , CAT-CaAl 0.5 Ta 0.5 O 3 , LA-LaAlO 3 ).…”

“…23 Observed longitudinal and transversal stresses in Ni/Si(111) cantilever exhibit a positive sign in both cases. That agrees well with the previous room temperature data 24 thus confirming the reliability of our experiment. The measurements were then performed on La 0.7 Sr 0. λ , is calculated to be 1565 ppm at the magnetic field of 12 T. This is comparable to the magnetostriction of polycrystalline bulk samples.…”

Magnetoelastic properties of epitaxial holmium and erbium thin films

“…The line is a fit to Callen's law B ␥,2 (T) ϭB ␥,2 (0)Î 5/2 ͓L Ϫ1 (m(T))͔, 20 where m is the reduced magnetization of the Ho film (mϭM (T)/M (0)), Î 5/2 is the reduced hyperbolic Bessel function, I lϩ 1 2 /I 1 2 of order lϭ2, and L Ϫ1 is the inverse Langevin function. 4 The optical method to measure magnetoelastic stresses used successfully at room temperature 22 is, to our knowledge, too far to be applicable at liquid helium temperatures, where the magnetism of rare earths deserve large attention. 5 The approximation of a flat cantilever used by us overestimates the value of B ␥,2 , as can be inferred from the numerical study performed by Watts et al 21 for a cantilever coated with a film of known magnetostrictive constant .…”

Comparing theory with experimental data in studying the deformation of magnetically smart films deposited on nickel and glass substrates

“…The simulation results were close to the calculated ones from the experiments for the sample of coated glass. In the derivation of the Equation (3) [13][14][15] , some assumptions were employed, and the effects of boundary conditions were not considered sufficiently. It is noted that the boundary effects play an important role when the specimen is shorter.…”