Co ∕ Cu ∕ Ir Mn films were irradiated with 40keV He+ ions varying the fluence and the current, with magnetic field applied at 120° with respect to the original exchange-bias direction. The angular variations of the exchange-bias field of the irradiated samples were compared with those of the as-made and the thermally annealed films. Gradual deviation of the exchange-bias direction with the fluence increase was observed. Complete reorientation of the easy axes of both ferromagnet and antiferromagnet toward that of the field applied during irradiation was achieved for fluences higher than 1×1015ions∕cm2, accompanied with a significant enhancement of the exchange-bias field.
Negative rotatable anisotropy is estimated via ferromagnetic resonance measurements in as-made, annealed, and ion-irradiated IrMn 3 /Ni 81 Fe 19 bilayers. Opposite to previous observations, inverse correlation between rotatable anisotropy and coercivity is observed. The exchange-bias field, determined from hysteresis loop measurements, is higher than that obtained from ferromagnetic resonance for all samples. The results are discussed in terms of majority antiparallel coupling and magnetic-field-induced transitions from antiparallel to parallel states of uncompensated spins at ferromagnet/antiferromagnet interface. We affirm that an observation of negative rotatable anisotropy evidences antiparallel coupling even in systems presenting conventional exchange bias. V C 2015 AIP Publishing LLC. [http://dx
The present work reports on the influence of ion irradiation in exchange-coupled bilayers. Magnetron-sputtered IrMn4/Co films were irradiated with 40 keV He+ ions and the dependence of their magnetic properties was studied as function of ion fluence and current used during the irradiations. The effects of ion damage and electronic excitation were also studied through additional irradiations with H+ and Ne+ ions. The results show a clear dependence of the exchange-bias field on the defects caused by the ion bombardment. No correlations with other irradiation effects were observed.
In situ X-ray absorption spectroscopy and mass spectrometry measurements were employed to simultaneously probe the atom specific short range order and reactivity of Pd and PtPd nanoparticles towards NO decomposition at 300 °C. The nanoparticles were synthesized by a well controlled, eco-friendly wet chemical reduction of metal salts and later supported on activated carbon. Particularly for the bimetallic PtPd samples, distinct atomic arrangements were achieved using a seeding growth method, which allowed producing a random nanoalloy, or nanoparticles with Pt- or Pd-rich core. X-ray photoelectron spectroscopy, transmission electron microscopy, and X-ray diffraction provided additional insights on their electronic, morphological and long range order structural properties. The results revealed that the higher the thermal induced atomic migration observed within the nanoparticles during thermal treatments, the least were their reactivity for NO abatement.
Spin-glass-like freezing in spin-chain compounds Ca3Co2−xMnxO6: Effect of disorder J. Appl. Phys. 112, 103923 (2012) Magnetoelectric coupling in La0.6Ca0.4MnO3-Bi0.6Nd0.4TiO3 composite thin films derived by a chemical solution deposition method Appl. Phys. Lett. 101, 212902 (2012) Areal density limitation in bit-patterned, heat-assisted magnetic recording using FePtX media J. Appl. Phys. 112, 093920 (2012) Hard ferromagnetism in melt-spun Hf2Co11B alloys Appl. Phys. Lett. 101, 202401 (2012) Electrically induced decrease of magnetization in Ca3Mn2O7 Appl. Phys. Lett. 101, 192407 (2012) Additional information on J. Appl. Phys. (NiCu) is lower than the blocking temperature of the AF (IrMn). Samples were either annealed or irradiated with He, Ar, or Ge ions at 40 keV. Due to the exchange coupling at the FM/AF interface, the coercivity (H C ) of the as-deposited FM/AF bilayer is rather higher than that of the corresponding FM single layer. We found that by choosing a proper ion fluence or annealing temperature, it is possible to controllably vary H C . Ion irradiation of the FM single layer has lead to only a decrease of H C and annealing or He ion irradiation has not caused important changes at the FM/AF interface; nevertheless, a twofold increase of H C was obtained after these treatments. Even more significant enhancement of H C was attained after Ge ion irradiation and attributed to ion-implantation-induced modification of only the FM layer; damages of the FM/AF interface, on the other hand, decrease the coercivity. V C 2012 American Institute of Physics. [http://dx
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