Tuning the ferromagnetic-antiferromagnetic interfaces of granular Co-CoO exchange bias systems by annealing

Abstract

Improvement of magnetic particle stability upon annealing in an exchange-biased nanogranular system J. Appl. Phys. 100, 064312 (2006) The low-temperature magnetic behavior of granular Co-CoO exchange bias systems, prepared by oxygen ion implantation in Co thin films and subsequent annealing, is addressed. The thermal activation effects lead to an O migration which results in virtually pure Co areas embedded in a structurally relaxed and nearly stoichiometric CoO phase. This yields decreased training and exchange bias shifts, while the blocking temperature significantly increases, coming close to the Neel temperature of bulk CoO for samples implanted to a fluence above 1 Â 10 17 ions/cm 2 (15% O). The dependence of the exchange bias shift on the pristine O-implanted content is analogous to that of the antiferromagnetic thickness in most ferromagnetic/antiferromagnetic systems (i.e., an increase in the exchange bias shift up to a maximum followed by a decrease until a steady state is reached), suggesting that, after annealing, the enriched Co areas might be rather similar in size for samples implanted above 1 Â 10 17 ions/cm 2 , whereas the corresponding CoO counterparts become enlarged with pristine O content (i.e., effect of the antiferromagnet size). This study demonstrates that the magnetic properties of granular Co-CoO systems can be tailored by controllably modifying the local microstructure through annealing treatments. V C 2014 AIP Publishing LLC. [http://dx

Angular Dependence of Exchange Bias and Magnetization Reversal Controlled by Electric‐Field‐Induced Competing Anisotropies

“…On the other hand, as shown in the previous reports, relative orientation of the unidirectional and uniaxial anisotropies was tuned by annealing with varying magnetic fi eld direction, [ 5,8,9 ] which could introduce other effects such as unwanted thermally induced diffusion. [ 8,33 ] Whereas, in our work these problems can be avoided by using one sample. Thus, we demonstrate that the combination of exchange-biased systems and ferroelectric materials offers a simple and effective way to investigate exchange bias, which is an important issue and its origin is still unclear, [1][2][3] using one sample with different ratios and relative orientations of the anisotropies controlled by electric fi elds and it will be very useful for the study of the exchange bias involving various systems including some novel materials.…”

Large Magnetoelectric Effects in Electrodeposited Nanoporous Microdisks Driven by Effective Surface Charging and Magneto-Ionics

“…58 The partial reduction from CoO to Co is consistent with the increase of the Kerr amplitude signal shown in Figure 3 since nanostructured CoO is likely paramagnetic at room temperature (note that bulk CoO has a Neél temperature of around 291 K). 59,60 2.4. Electron Energy Loss Spectroscopy (EELS) Characterization.…”

Influence of Superparamagnetism on Exchange Anisotropy at CoO/[Co/Pd] Interfaces

“…Our research was carried out on [CoO/Co/Pd] 10 polycrystalline multilayer. In this structure the AFM/FM CoO/Co interface is a model system for the exchange bias phenomena investigations [10][11][12] , and is responsible for introducing the exchange anisotropy. The perpendicular magnetic anisotropy, important for applications of the exchangebiased systems in data storage and memories, is implemented in the Co-Pd interface in multilayers or alloys.…”