We have used a simple self-aligned process to fabricate magnetic tunnel junctions down to submicron sizes. Optical and electron-beam lithographies were used to cover a range of areas spanning five orders of magnitude. The bottom magnetic electrodes (Co or permalloy) in our junctions were exchange biased by an antiferromagnetic layer (MnFe). The top electrodes were made of soft magnetic materials (Co or permalloy). We have consistently obtained large magnetoresistance ratios (15%–22%) at room temperature and in fields of a few tens of Oe. The shape of the field response of the magnetoresistance was varied from smooth to highly hysteretic by adjusting the shape anisotropy of one junction electrode.

We report on the fabrication of a new class of trilayer epitaxial thin film devices based on the doped perovskite manganates La–Ca–Mn–O and La–Sr–Mn–O. We show that large resistance changes, up to a factor of 2, can be induced by a moderate applied magnetic field below 200 Oe in these trilayers supporting current-perpendicular-to-plane transport. These results show that low-field spin-dependent transport in manganates can be accomplished, the magnitude of which is suitable for magnetoresistive field sensors.

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We have measured and simulated the dynamics of magnetization reversal in 5 nm by 0.8 by 1.6 mm Ni 60 Fe 40 thin films. The films measured form the upper electrode of a spin-polarized tunnel junction so that the magnetization direction of the film can be probed by measuring the tunneling resistance of the junction. When a magnetic field pulse is applied, the time to switch the film magnetization changes from greater than 10 ns to less than 500 ps as the pulse amplitude is increased from the coercive field to 10 mT and beyond. We have simulated these transitions using micromagnetic modeling of the exact experimental conditions. The simulations agree well with the experimental measurements. [S0031-9007(98)07661-3] PACS numbers: 75.70.AkIn this paper we will investigate the dynamics of magnetization reversal in micron-sized magnets. This will be done both from measurement and modeling points of view. While the switching times of small ferromagnetic objects have been measured many times in the past [1], none of these earlier measurements were made in micronsized objects with picosecond time resolution. Recently several groups have made picosecond time resolution measurements using magneto-optic [3] or inductive probing [2] of the sample magnetization on larger samples. Also, while there has been widespread use of micromagnetic modeling to study the static properties of small structures, time domain simulations of how such micron-sized structures switch are rare [4]. As far as we know, this is the first paper where both measured and simulated dynamical properties are quantitatively compared on micronsized magnetic samples.In order to measure the magnetization reversal in micron-sized films, we chose to use spin-polarized tunneling as a probe of the magnetization direction. In this way, a simple-to-measure change in the tunneling resistance between a pinned and a free magnetic layer can serve to probe the magnetization dynamics of a micron-sized magnetic film. Using this method, we have measured the time required to reverse the magnetization direction in micron and submicron-sized thin films of a soft ferromagnet Ni 60 Fe 40 in the 100 ps to 100 ns range. In order to understand and visualize the dynamics of the magnetization reversal in such films we have developed time-domain micromagnetic models of the experimentally measured films that exactly simulate the experimental conditions. By comparing the results of the simulations with the measurements, the simulations can be vetted and some of the needed parameters can be determined.The sample structure consisted of two thin ferromagnetic films separated by an Al 2 O 3 tunnel junction [5]. The bottom film, the pinned layer, was an antiparallel (AP) pinned structure formed of two Co layers separated by a 0.6 nm Ru film. The top film, the free layer, was a 5 nm layer of Ni 60 Fe 40 . The structures reported here were all 0.8 by 1.6 mm in size, but both smaller and larger ones were also tested. There was a uniaxial anisotropy of approximately 800 J͞m 3 along the easy (long) a...

What is a genre? Which films are genre films? How do we know to which genre they belong? As fundamental as these questions may seem, they are almost never asked-let alone answered-in the field of cinema studies. Most comfortable in the seemingly uncomplicated world of Hollywood classics, genre critics have felt little need to reflect openly on the assumptions underlying their work. Everything seems so clear. Why bother to theorize, American pragmatism asks, when there are no problems to solve? We all know a genre when we see one. Scratch only where it itches. According to this view, genre theory would be called for only in the unlikely event that knowledgeable genre critics disagreed on basic issues. The task of the theorist is then to adjudicate among conflicting approaches, not so much by dismissing unsatisfactory positions but by constructing a model that reveals the relationship between differing critical claims and their function within a broader cultural context. Whereas the French clearly view theory as a first principle, we Americans tend to see it as a last resort, something to turn to when all else fails. Even in this limited, pragmatic view, whereby theory is to be avoided at all costs, the time for theory is nevertheless upon us. The clock has struck thirteen; we had best call in the theoreticians. The more genre criticism I read, the more uncertainty I note in the choice or extent of essential critical terms. Often what appears as hesitation in the terminology of a single critic will turn into a clear contradiction when studies by two or more critics are compared. Now, it would be one thing if these contradictions were simply a matter of fact. On the contrary, however, I suggest that these are not temporary problems, bound to disappear as soon as we have more information or better analysts. Instead, these uncertainties reflect constitutive weaknesses of current notions of genre. Three contradictions in particular seem worthy of a good scratch. When we establish the corpus of a genre we generally tend to do two things at once, and thus establish two alternate groups of texts, each corresponding to a different notion of corpus. On the one hand, we have an

We show that shape anisotropy can be used to control the response characteristics of magnetic tunnel junctions. By varying the junction shape, the resistance versus field curve was made to vary from a nonhysteretic linear curve with a high-field sensitivity (0.3%/Oe) to a hysteretic response curve with high squareness.

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We have studied systematically the magnetotunneling properties of several metallic magnetictunnel-junction systems (Ni80Fe20–insulator–Ni80Fe20,Ni80Fe20–I–Co,Co–I–Co, Ni40Fe60–I–Co). The room-temperature magnetoresistance MR value at zero-bias ranges between 16% and 27%, depending on the spin polarization of the electrodes. There seems to be a general bias dependence of MR in all of these systems. In particular, it requires a bias in the range of 0.22–0.23 V to suppress the maximum MR value by half. We have also measured the bias dependence of MR as a function of barrier parameters (thickness and oxidation time). At low temperature, a sharp cusplike feature appears near zero bias. In some cases, low-temperature MR values substantially exceed expectations from established spin-polarization.