Harnessing the electron's second fundamental property, its spin, is the basis of spintronic phenomena and devices [1] . These include recently discovered phenomena like the quantum anomalous Hall effect [2] in magnetic topological insulators [3] , spin transfer torque [4,5] effects in nonmagnetic metal / ferromagnetic metal / oxide heterostructures and spin transfer torque (SOT) switching of ferromagnets [6,7] , and ultimately of FMIs [8] . To realize novel circuit devices based on these effects a rich variety of specifically tailored magnetic materials has still to be developed. For instance, the study of exotic phenomena occurring at the boundary of topological insulators with ferromagnets requires the latter to be insulating, yet to retain magnetic properties including PMA.One of the most prominent FMIs classes is that of iron garnets, of which the most well studied is Y 3 Fe 5 O 12 (YIG). The ultra low magnon damping characteristics [9] and magneto-optical properties [10,11] of YIG are well known. The former makes YIG a suitable candidate for spin wave logic [12] and signal transmitters [13] due to the extremely large magnon decay length of several tens of millimeters. Epitaxial YIG thin films can, in principle, also possess PMA as a result of magnetization-lattice coupling [14] for thicknesses below nm [15,16] , but the fabrication of YIG films with complete out-of-plane remanence remains elusive because of its low magnetocrystalline anisotropy and magnetoelastic coefficients. In contrast, 50 nm thick thulium iron garnet (Tm 3 Fe 5 O 12 , TmIG), has been reported to show PMA [17,18] caused by magnetoelastic anisotropy when grown epitaxially on (111)-oriented gallium gadolinium garnet (Gd 3 Ga 5 O 12 or GGG) [19] .We recently demonstrated [8] reversible magnetization switching in 8 nm thick TmIG by utilizing SOT from an adjacent platinum layer, but a detailed structural and magnetic characterization of TmIG in the few-nm thickness regime is still lacking. In the present article, we provide a comprehensive description of the structural characteristics and magnetic properties of TmIG/GGG down to a thickness of nm. Furthermore we demonstrate that efficient spin transport can be achieved through the TmIG/Pt interface by measuring spin Hall magnetoresistance (SMR) in Pt. We exploit this method to measure the anisotropy field of the strained TmIG film electrically, which is inaccessible by conventional magnetometry measurements due to the dominant paramagnetic contribution of the GGG substrate. These results emphasize the potential of TmIG as a spintronic material.Structural characterization of the TmIG films are summarized in Fig.1. With xray reflectometry (XRR) scans (not shown), we measured film thicknesses of PMA epitaxial TmIG down to nm nm . To quantify the strain state of TmIG via XRD we measured a nm thick TmIG film, since thinner films could not be resolved with enough intensity using high resolution XRD. The symmetric XRD spectra shown in Fig.1a demonstrates a fully strained film with lattice spacing of ...

Perpendicular magnetic anisotropy [Co/Pd]15 and L10-FePt nanowire arrays of period 63 nm with linewidths 38 nm and 27 nm and film thickness 27 nm and 20 nm respectively were fabricated using a self-assembled PS-b-PDMS diblock copolymer film as a lithographic mask. The wires are predicted to support Néel walls in the Co/Pd and Bloch walls in the FePt. Magnetostatic interactions from nearest neighbor nanowires promote a ground state configuration consisting of alternating up and down magnetization in adjacent wires. This was observed over ∼75% of the Co/Pd wires after ac-demagnetization but was less prevalent in the FePt because the ratio of interaction field to switching field was much smaller. Interactions also led to correlations in the domain wall positions in adjacent Co/Pd nanowires. The reversal process was characterized by nucleation of reverse domains, followed at higher fields by propagation of the domains along the nanowires. These narrow wires provide model system for exploring domain wall structure and dynamics in perpendicular anisotropy systems.

We present a study on perpendicular magnetic tunnel junctions with W as buffer and capping layers. A tunneling magnetoresistance of 138% and an interfacial magnetic anisotropy of 1.67 erg/cm 2 were obtained in optimally annealed samples. However, after extended annealing at 420 C, junctions with W layers showed extremely small resistance due to interdiffusion of W into the MgO barrier. In contrast, in Ta-based junctions, the MgO barrier remained structurally stable despite disappearance of magnetoresistance after extended annealing due to loss of perpendicular magnetic anisotropy. Compared with conventional tunnel junctions with in-plane magnetic anisotropy, the evolution of tunneling conductance suggests that the relatively low magnetoresistance in perpendicular tunnel junctions is related to the lack of highly polarized D 1 conducting channel developed in the initial stage of annealing.

Voltage control effects provide an energy-efficient means of tailoring material properties, especially in highly integrated nanoscale devices. However, only insulating and semiconducting systems can be controlled so far. In metallic systems, there is no electric field due to electron screening effects and thus no such control effect exists. Here we demonstrate that metallic systems can also be controlled electrically through ionic not electronic effects. In a Pt/Co structure, the control of the metallic Pt/Co interface can lead to unprecedented control effects on the magnetic properties of the entire structure. Consequently, the magnetization and perpendicular magnetic anisotropy of the Co layer can be independently manipulated to any desired state, the efficient spin toques can be enhanced about 3.5 times, and the switching current can be reduced about one order of magnitude. This ability to control a metallic system may be extended to control other physical phenomena. (a) EF x z H z

Development of novel magnetic materials is of interest for fundamental studies and applications such as spintronics, permanent magnetics, and sensors. We report on the first experimental realization of single element ferromagnetism, since Fe, Co, and Ni, in metastable tetragonal Ru, which has been predicted. Body-centered tetragonal Ru phase is realized by use of strain via seed layer engineering. X-ray diffraction and electron microscopy confirm the epitaxial mechanism to obtain tetragonal phase Ru. We observed a saturation magnetization of 148 and 160 emu cm−3 at room temperature and 10 K, respectively. Control samples ensure the ferromagnetism we report on is from tetragonal Ru and not from magnetic contamination. The effect of thickness on the magnetic properties is also studied, and it is observed that increasing thickness results in strain relaxation, and thus diluting the magnetization. Anomalous Hall measurements are used to confirm its ferromagnetic behavior.