We have investigated the structure and magnetization of Co2(Cr1−xFex)Al (0 ⩽ x ⩽ 1) and Co2FeSi full-Heusler alloy films deposited on thermally oxidized Si (SiO2) and MgO (001) single crystal substrates by ultra-high vacuum sputtering at various temperatures. The films were also post-annealed after deposition at room temperature (RT). Magnetic tunnel junctions with a full-Huesler alloy electrode were fabricated with a stacking structure of Co2YZ (20 nm)/Al (1.2 nm)-oxide/Co75Fe25 (3 nm)/IrMn (15 nm)/Ta (60 nm) and microfabricated using electron beam lithography and Ar ion etching with a 102 µm2 junction area, where Co2YZ stands for Co2(Cr1−xFex)Al or Co2FeSi. The tunnel barriers were formed by the deposition of 1.2 nm Al, followed by plasma oxidization in the chamber. The x-ray diffraction revealed the A2 or B2 structure depending on heat treatment conditions and the substrate, but not L21 structure for the Co2(Cr1−xFex)Al (0 ⩽ x ⩽ 1) films. The L21 structure, however, was obtained for the Co2FeSi films when deposited on a MgO (001) substrate at elevated temperatures above 473 K. The maximum tunnelling magnetoresistance (TMR) was obtained with 52% at RT and 83% at 5 K for a junction using a Co2(Cr0.4Fe0.6)Al electrode. While the junction using a Co2FeSi electrode with the L21 structure exhibited the TMR of 41% at RT and 60% at 5 K, which may be improved by using a buffer layer for reducing the lattice misfit between the Co2FeSi and MgO (001) substrate.

The tunnel magnetoresistance (TMR) effect has been investigated for magnetic tunnel junctions with epitaxial Co2FeAl0.5Si0.5 Heusler electrodes with B2 and L21 structures on a Cr-bufferd MgO substrate. The epitaxially grown Co2FeAl0.5Si0.5 has B2 structure when annealed below 400°C, and has L21 structure for annealing above 450°C. The TMR ratio of 76% at room temperature and 106% at 5K were obtained for a MgO(001)∕Cr∕B2-type Co2FeAl0.5Si0.5∕Al oxide/Co75Fe25∕IrMn∕Ta. The TMR ratio is larger than that of magnetic tunnel junction with an L21-type electrode, which may be due to the smoother surface of the B2 structure and disordered L21 structure due to the Cr atom interdiffusion.

Magnetic tunnel junctions (MTJs) with a Co2FeAl Heusler alloy electrode are fabricated by the deposition of the film using an ultrahigh vacuum sputtering system followed by photolithography and Ar ion etching. A tunnel magnetoresistance (TMR) of 47% at room temperature (RT) are obtained in a stack of Co2FeAl∕Al–Ox∕Co75Fe25 magnetic tunnel junction (MTJ) fabricated on a thermally oxidized Si substrate despite the A2 type atomic site disorder for Co2FeAl. There is no increase of TMR in MTJs with the B2 type Co2FeAl, which is prepared by the deposition on a heated substrate. X-ray photoelectron spectroscopy (XPS) depth profiles in Co2FeAl single layer films reveal that Al atoms in Co2FeAl are oxidized preferentially at the surfaces. On the other hand, at the interfaces in Co2FeAl∕Al–Ox∕Co75Fe25 MTJs, the ferromagnetic layers are hardly oxidized during plasma oxidation for a formation of Al oxide barriers.

We have investigated the crystal structure and magnetic moment of the Co2FeAl and Co2FeSi films deposited onto thermally oxidized Si and MgO(100) single-crystal substrates, and the structural effect on the tunnel magnetoresistance (TMR) of the magnetic tunnel junctions (MTJs) using a Co2FeZ (Z=Al or Si). The structure was changed by the substrate and postannealing temperatures, in which the fully epitaxial and polycrystalline Co2FeAl and Co2FeSi films were obtained with the different disorder structure. The magnetic moment of Co2FeAl films was found to be uninfluenced by the crystal structure. Spin-valve-type MTJs consisting of Co2FeZ(100nm)∕Al(1.2nm)-oxide∕Co75Fe25(2nm)∕IrMn(10nm)∕Ta(60nm) were fabricated (Z=Al or Si) on thermally oxidized Si and MgO(100) single-crystal substrates. The maximum TMR obtained is about 50% at room temperature for MTJs with Co2FeAl films, regardless of the crystal structure of Co2FeAl.

Icing is still one of the most common treatments to acute skeletal muscle damage in sports medicine. However, previous studies using rodents reported the detrimental effect of icing on muscle regeneration following injury. This study aimed to elucidate the critical factors governing the impairment of muscle regeneration by icing with a murine model of eccentric contraction-induced muscle damage by electrical stimulation. Because of icing after muscle injury, the infiltration of polynuclear and mononuclear cells into necrotic muscle fibers was retarded and attenuated, leading to the persistent presence of necrotic cellular debris. These phenomena coincided with the delayed emergence and sustained accumulation of Pax7+ myogenic cells within the regenerating area. Additionally, due to icing, delayed and/or sustained infiltration of M1 macrophages was noted in accordance with the perturbed expression patterns of inflammation-related factors, including tumor necrosis factor-α (TNF-α) and interleukin-10 (IL-10). The key myogenic regulatory factors (i.e., MyoD and myogenin) involved in the activation/proliferation and differentiation of myogenic precursor cells were not altered by icing during the regenerative process. A detailed analysis of regenerating myofibers by size distribution at day 14 after muscle damage showed that the ratio of small regenerating fibers to total regenerating fibers was higher in icing-treated animals than in untreated animals. These findings suggest that icing following muscle damage blunts the efficiency of muscle regeneration by perturbing the removal of necrotic myofibers and phenotypic dynamics of macrophages rather than affecting myogenic factors.