Introductory Physics 1A

Exam paper (Supplementary) for second semeste

Influence of growth morphology on the Neel temperature of CrRu thin films and heterostructures

Dimensionality effects on epitaxial and polycrystalline Cr1-xRux alloy thin films and in Cr/Cr–Ru heterostructures are reported. X-ray analysis on Cr0.9965Ru0.0035 epitaxial films indicates an increase in the coherence length in growth directions(100) and (110) with increasing thickness(d), in the range 20≤d≤300nm. Atomic force microscopy studies on these films show pronounced vertical growth for d>50nm, resulting in the formation of columnar structures. The Néel temperatures (TN) of the Cr0.9965Ru0.0035 films show anomalous behaviour as a function of d at thickness d≈50 nm. It is interesting to note that this thickness corresponds to that for which a change in film morphology occurs. Experiments on epitaxial Cr1-xRux thin films, with 0≤x≤0.013 and d = 50 nm, give TN–x curves that correspond well with that of bulk Cr1-xRux alloys. Studies on Cr/Cr0.9965Ru0.0035 superlattices prepared on MgO (100), with the Cr layer thickness varied between 10 and 50nm, keeping the Cr0.9965Ru0.0035 thickness constantat 10nm, indicate a sharp decrease in TN as the Cr separation layers reaches a thickness of 30nm; ascribed to spin density wave pinning in the Cr layers for d< 30nm by the adjacent CrRu layers

Electrical Manipulation of Magnetic Anisotropy in a Fe 81 Ga 19 / Pb ( Mg 1 / 3 Nb 2 / 3 ) O 3 - Pb ( Zr x Ti 1 − x ) O 3 Magnetoelectric Multiferroic Composite

International audienc

Thickness dependence of magnetization reversal and magnetostriction in Fe 81 Ga 19 thin films

International audienc

Magnetization Reversals of Fe 81 Ga 19 -Based Flexible Thin Films Under Multiaxial Mechanical Stress

International audienceThe effect of multiaxial mechanical stress on angle-dependent magnetization reversals is studied on a single 10-nm Ni80Fe20 film, a single 10-nm Fe81Ga19 film, and a Ni80Fe20(10 nm)/Fe81Ga19(10 nm) bilayer. These films are grown on flexible Al “kitchenlike” foils. These flexible foils are bent on two convex optical lenses to apply multiaxial mechanical stresses of different magnitudes. In order to understand the mechanisms driving the physical properties of the flexible systems, the magnetic films are also grown on hard native-oxide-covered Si(100) substrates. By probing the angular dependence of the coercive field and the remanent magnetization, we show that the Ni80Fe20 single layer and the Ni80Fe20/Fe81Ga19 bilayer grown on Si present a uniaxial anisotropy. Along their easy axis, their domain structure at the coercive field exhibits large domains with sawtooth domain walls. However, the Fe81Ga19 layer grown on Si shows a cubic anisotropy and sharp domain walls with a right-angle geometry along its easy axis. All layers grown on Al foils show development or enhancement of a uniaxial anisotropy arising from the Al surface morphology. Multiaxial mechanical stress applied to the flexible Al foils results in very different nonreversible effects as a function of the composition of the layered system. For Ni80Fe20, multiaxial mechanical stress has no effect, as expected for a nonmagnetostrictive system. For Fe81Ga19, it results in a full in-plane randomization of its magnetization-reversal properties. For the bilayer, multiaxial mechanical stress does not fully randomize the in-plane magnetization-reversal properties: the bilayer retains a uniaxial character