M. Ciria

Strong interfacial magnetoelastic stress in holmium - lutetium (0001) superlattices

The saturation magnetoelastic stress (MS), , breaking the basal plane cylindrical symmetry of the hexagonal structure, has been measured for the series of superlattices (n = 8 to 85 atomic planes, with separation c/2). The MS was directly measured using a low-temperature cantilever technique. The Ho block MSs in the superlattices are larger than in an Ho film of A thickness and in bulk Ho. An analysis accounting for the contributions to coming from: the volume, , the interface, with magnetoelastic parameter , and the epitaxial strain shows that the interfacial magnetoelastic stress is strong, up to about six times larger than for n = 8, and of the opposite sign.

Magnetoelastic study of Ho/Y and Ho/Lu metallic superlattices

Abstract Magnetoelastic stress measurements in Ho/Y and Ho/Lu superlattices were performed by using a capacitive cantilever technique. The magnetic phase diagrams obtained from in-field transitions observed in the stress isotherms show helical, fan and ferromagnetic phases. At zero-field, the ferromagnetic phase is suppressed in Ho/Y and stabilised in Ho/Lu. Magnetoelastic coupling coefficients corresponding to the breaking of the cylindrical symmetry of the basal plane have been determined. Surface magnetostriction is observed for {Ho 31 Lu 19 } 50 .

Macroscopic random magnetic anisotropy constant in crystalline DyxY1−xAl2 (x=0.3, 0.4)

Cooling in a weak magnetic field the random magnetic anisotropy (RMA) spin glasses DyxY1−xAl2 (x=0.3, 0.4) induces unidirectional and uniaxial anisotropies, on top of the cubic coherent one. The unidirectional anisotropy constant KRMAu has been determined at 3.8 K, amounting at zero applied field 127 and 255 J/m3 for x=0.3 and 0.4, respectively. The predicted model ratio between KRMAu and the uniaxial constant KRMAa, i.e., KRMAa=2KRMAu, has been confirmed. As by‐product the relevant RMA parameter D2/J, where D is the RMA crystal field strength and J, the exchange constant has been determined, as well as separate estimates of D and J.

Magnetoelasticity of single-crystal (110) SmFe2 thin-film

Abstract The magnetoelastic behaviour of a 5000xa0A thick single-crystal (1xa01xa00) SmFe2 thin-film has been investigated by performing MEL stress measurements between 10 and 290xa0K, and up to 12xa0T as the maximum applied magnetic field. Thus, the direct measurement of the [1 1 1] rhombohedral stress, b2, is possible by applying magnetic field along the in-plane direction and measuring the resulting stress longitudinal and transversely to the applied magnetic field (H||[1 1 1]) . The b2 coefficient is positive and its values are of the same order of magnitude as those in the bulk, for the entire range of studied temperatures. The thermal dependence of b2 magnetoelastic stress can be ascribed to the distortion of the crystal-electric-field around Sm+3. The effect of the internal strain on the b2 magnetoelastic stress parameter will be interpreted as a second-order contribution to the magnetoelastic stress coefficient in the total magnetoelastic energy of the thin film.

Magnetic and magnetoelastic properties of epitaxial SmFe2 thin film

We report on magnetic and magnetoelastic measurements for a 5000 Å (110) SmFe(2) thin film, which was successfully analyzed by means of a point charge model for describing the effect of the epitaxial growth in this kind of system. Some of the main conclusions of the Mössbauer and magnetoelastic results and the new magnetization results up to 5 T allow us to get a full description of the crystal electric field, exchange, and magnetoelastic behavior in this compound. So, new single-ion parameters are obtained for the crystal field interaction of samarium ions, A(4)(r(4)) = +755 K/ion and A(6)(r(6)) = -180 K/ion, and new single-ion magnetoelastic coupling B(γ,2) is approximately equal -200 MPa and B(ε,2) is approximately equal MPa, which represent the tetragonal and the in-plane shear deformations, respectively. Moreover, the new thermal behavior of the samarium magnetic moment, the exchange coupling parameter, and the magnetocrystalline anisotropy of the iron sublattice are obtained too. From these, the softening of the spin reorientation transition with respect to the bulk case could be accounted for.