sputter-growth-characterization-metamagnetic-b2-ordered-ferh

Sputter Growth and Characterization of Metamagnetic B2-ordered FeRh Epilayers

Chemically ordered alloys are useful in a variety of magnetic nanotechnologies. They are most conveniently prepared at an industrial scale using ...

University of Leeds

Exchange bias is commonly manifested as the hysteresis-loop shift observed when a ferromagnet is in contact with an antiferromagnet. Here, we report observations of exchange bias with unusual features of a ferromagnet in contact with a spin glass, demonstrating that this is a phenomenon of greater generality. The easily measured properties of the ferromagnet allow access to the internal magnetic degrees of freedom of the glass to which they are coupled. Our results show that a Co/CuMn bilayer system exhibits all the rich phenomena of coercivity enhancement, bias-field shifts and training effects associated with a conventional ferromagnet/antiferromagnet system. Nevertheless, striking differences arise, such as an orientation reversal of the bias field in a small temperature range just below the blocking temperature. We argue that all features can be understood within the context of a random-field model for long-ranged oscillatory Ruderman-Kittel-Kasuya-Yosida (RKKY) coupled spins.

Exchange bias using a spin glass.

Single electron electronics is now well developed, and allows the manipulation of electrons one-by-one as they tunnel on and off a nanoscale conducting island. In the past decade or so, there have been concerted efforts in several laboratories to construct single electron devices incorporating ferromagnetic components in order to introduce spin functionality. The use of ferromagnetic electrodes with a non-magnetic island can lead to spin accumulation on the island. On the other hand, making the dot also ferromagnetic introduces new physics such as tunnelling magnetoresistance enhancement in the cotunnelling regime and manifestations of the Kondo effect. Such nanoscale islands are also found to have long spin lifetimes. Conventional spintronics makes use of the average spin-polarization of a large ensemble of electrons: this new approach offers the prospect of accessing the quantum properties of the electron, and is a candidate approach to the construction of solid-state spin-based qubits.

Single electron spintronics.

We report the observation of a large linear magnetoresistance in the ohmic regime in commonplace commercial n-type silicon wafer with a P dopant density of (1.4Â±0.1) Ã—10(15) cm(-3), and report measurements of it in the temperature range 30-200 K. It arises from the deformation of current paths, which causes a part of the Hall field to be detected at the voltage probes. In short, wide samples we found linear magnetoresistance as large as 4707% in an 8 tesla field at 35 K. Sample geometry effects like these are commonplace in commercial Hall sensors. However, we found that the effect persisted in long, thin samples where the macroscopic current flow should be uniform between the voltage probes: we observed a magnetoresistance of 445% under the same conditions as above. We interpret this result as arising due to spatial fluctuations in the donor density, in the spirit of the Herring model.

Article	Year
Exchange bias using a spin glass. Nature materials\| PubMed ID: 17173030	2007
Single electron spintronics. Philosophical transactions. Series A, Mathematical, physical, and engineering sciences\| PubMed ID: 21727119	2011
Linear magnetoresistance in n-type silicon due to doping density fluctuations. Scientific reports\| PubMed ID: 22876340	2012

Christopher H. Marrows

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