Anodic alumina membranes with modulated pore diameters serve as template for the preparation of magnetic nanowires. Filling the pores with Ni by electrodeposition delivers wires replicating the variation in modulation in pore diameter from 80 to 160 nm. Such structures are of interest for the observation and control of magnetic domain wall motion. Single-object characterization utilizing the magneto-optical Kerr effect magnetometry evidences a strong correlation between geometric parameters and magnetic properties. Ensemble magnetization measurements with a superconducting quantum interference device show the effect of dipolar interactions. Analytical models can reproduce the lowering of coercivity due to the presence of enhanced stray fields within the array. Magnetic force microscopy at individual wires indicates the presence of a strong stray field in the vicinity of the diameter change. The preparation technique demonstrates a mass production method of nano-objects with designed geometric irregularities, which could be used to control the motions of magnetic domain walls.

We present a photoemission electron microscopy method that combines magnetic imaging of the surface and of the inner magnetization in three-dimensional core-shell nanostructures. The structure investigated consists of a cylindrical nickel core that is completely surrounded by a shell of iron oxide and silicon oxide layers. The method enables one to image the magnetization configuration of the nickel core even though the shell is thicker than the mean-free path of the photoelectrons. Characteristic L 3 and L 2 edges can be observed not only in the yield of the photoelectrons emitted from the surface of the nanostructure but also in its shadow. X-ray magnetic circular dichroism in the electron yield of the x rays absorbed and transmitted by the multilayered nanowire allows for the individual imaging of the magnetization configurations of the iron oxide tube and the nickel core. The method suggests novel approaches for the characterization of the magnetic and material properties of complex three-dimensional nanostructures.

The phenomenon of different time scales of ultrafast demagnetization has attracted much attention. This so-called diversity of ultrafast demagnetization has been explained by the microscopic three temperature model (M3TM) and by the Landau-Lifshitz-Bloch model (LLBM). Here, we revisit the basic three temperature model (3TM) and provide a general criterion for explaining the different time scales observed. We focus on the role of magnetic heat capacity, which we find mainly determines the slowing down of the demagnetization time with increasing ambient temperature and laser fluence. In this context, we clarify the role of magnetic heat capacity in the M3TM and compare the 3TM with the LLBM. To illustrate the role of magnetic heat capacity, we present a simulation of ultrafast demagnetization of Ni. Furthermore, we present time-resolved magneto-optic Kerr effect measurements of ultrafast demagnetization and specific heat of Fe 46 Cu 6 Pt 48 from 300 K to close to its Curie temperature. While most of the prior experimental research used high-fluence laser pulses causing sizable temperature excursions of the sample, our experiments involve small temperature excursions, which are crucial for studying the role of magnetic heat capacity in ultrafast demagnetization. Our experimental results corroborate that the slowing down of ultrafast demagnetization is dominated by the increase of the magnetic heat capacity near the Curie temperature.

We report measurements of the cross-plane thermal conductivity of periodic Co/Cu multilayers using time-domain thermoreflectance. The cross-plane thermal conductivity increases from ∼ 18 W m −1 K −1 at remanence to ∼ 32 W m −1 K −1 at saturation fields. This giant magnetothermal resistance (GMTR) effect is consistent with predictions based on the Wiedemann-Franz law.We discuss the role of a spin-dependent temperature, known as spin heat accumulation, in GMTR experiments and develop a three-temperature model capable of predicting the time-evolution of the temperatures of majority-spin electrons, minority-spin electrons, and phonons subsequent to pulsed laser heating.

We use time-resolved magneto-optic Kerr effect (TR-MOKE) and ultrathin Co/Pt transducer films to perform thermal transport experiments with higher sensitivity and greater time resolution than typically available in studies of interfacial thermal transport by time-domain thermoreflectance (TDTR). We measure the interface conductance between Pt and amorphous SiO 2 using Pt/Co/Pt ferromagnetic transducer films with thicknesses between 4.2 nm and 8.2 nm and find an average value of G Pt ≈ 0.3 GW m −2 K −1 . This result demonstrates that interfaces between metals and amorphous dielectrics can have a conductance corresponding to Kapitza lengths of the order of 4 nm, and are thus of relevance when engineering nanoscale devices. For thin SiO 2 layers our method also provides sensitivity to the interface conductance between SiO 2 and Si and we find G Si ≥ 0.6 GW m −2 K −1 as the lower limit.