The influence of internal stress on the magnetic anisotropy and the magnetostriction was investigated in sputter-deposited amorphous (Tb0.27Dy0.73)0.42Fe0.58 films. Films with tensile stress show in-plane anisotropy and giant magnetostriction of λ∥=400×10−6 at 1 T measured in a field parallel to the film plane at room temperature. The magnetostriction rises rapidly to λ∥=200×10−6 at 0.05 T and the coercivity is less than 0.01 T. On the other hand films with compressive stress show perpendicular anisotropy and still higher magnetostriction of λ∥=540×10−6 at 1 T; however, this is by far a slower increase of magnetostriction at small fields. This different behavior is explained by considering the nature of magnetization processes, i.e., domain-wall motion and spin rotation.

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Although the 3ω method was originally introduced to measure the thermal conductivity of bulk material and was later developed further to include thin-film materials, many thermal and geometrical parameters influence the 3ω signal. We show that several of these parameters can be determined simultaneously from a single 3ω measurement. With the commonly used frequency range, however, some parameter combinations cannot be determined uniquely. To overcome this problem we have developed an electronic setup for measurements from 5 Hz up to 200 kHz. We show numerically and experimentally that we can determine four physical parameters from a single measurement in this frequency range. This makes the 3ω method very suitable for microelectronics and microsensor testing, where physical parameters should ideally be determined by purely electrical measurements.

Scanning micro-mirror actuators are silicon-based oscillatory micro-electro-mechanical systems (MEMS). They enable laser distance measurements for automotive LIDAR applications as well as projection modules for the consumer market. For MEMS applications, the geometric structure is typically designed to serve a number of functional requirements. Most importantly, the mode spectrum contains a single high-Q mode, the drive mode, which per design is expected to yield the only resonantly excited geometric motion during operation. Yet here, we report on the observation of a resonant three-mode excitation via a process known as spontaneous parametric down-conversion. We show that this phenomenon, most extensively studied in the field of nonlinear optics, originates from three-wave coupling induced by geometric nonlinearities. In combination with further Duffing-type nonlinearities, the micro mirror displays a variety of nonlinear dynamical behaviour ranging from stationary state bifurcations to dynamical instabilities observable via amplitude modulations. We are able to explain and emulate all experimental observations using a single fundamental model. In particular, our analysis allows us to understand the conditions for the onset of three-wave down-conversion which if not accounted for in the design of the MEMS structure, can have drastic impact on its functionality even leading to fracture.

The magnetic properties of (Tb0.27Dy0.73)xFe1−x dependent on composition and microstructure are investigated in the range of 0.2 ≦ x ≦ 0.46. Both amorphous and partially crystalline films are prepared by dc sputtering. Composition is determined by wavelength dispersive X‐ray, oxygen content, and depth profile by nuclear reaction analysis and Auger electron spectroscopy. All films show a giant magnetostriction up to λ ≈︁ 400 × 10−6 at an applied field of 1 T. A compensation minimum of polarization at room temperature was found for x ≈︁ 0.24. The amorphous films are characterized by an in‐plane easy axis of polarization, combined with a large in‐plane susceptibility for low applied magnetic fields. The coercivity of polarization and magnetostriction is below 10mT, the Curie temperature about 400 K. In contrast, the partially crystalline films show a coercivity of about 180 mT, a low susceptibility parallel as well as perpendicular to the film plane, and a Curie temperature of about 600 K.