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Newest Member Terry Bergin
Effects of a Uniform Applied Magnetic Field and Temperature on the Magnetic Properties of the Dipolar Anti-ferromagnetic planar System: Parametric Study
One important class of reduced dimensional magnetic materials is quasi two dimensional systems. The attractive features of this class of materials for both scientific and technological applications are referred to their magnetic
properties, which are different from those of their bulk counterparts.
This has recently led to significant technological applications such as magnetic sensors, recording and storage media.
Three important magnetic systems can be considered to be quasi two dimensional.The first is ultra thin magnetic films. Ultra thin magnetic films consist of several mono layers of magnetic atoms deposited on a non magnetic substrate, such as Ni on Cu(001) substrate. The magnetic
spins of such films are observed to be ordered at low temperatures, and show a variety of interesting ordered phases. Among these are the reorientation transitions of magnetization from out of plane to in plane either above critical temperature at constant film thickness [5, 6, 7, 8], or above critical film thickness at constant temperature [5, 6, 9, 10, 11]. A transition from in plane to out of plane has also been observed, as in Ni on
Cu(001) substrate and Gd on W(110) substrate [12, 13, 14].
A wide variety of magnetic patterns can also be stabilized in ultra thin magnetic films,because of the interplay between the perpendicular induced surface anisotropy, the exchange interaction, and the longrange dipolar interaction.
Nowadays ferromagnetic thin films are of great interest due to several reasons. First, their wide range of applications in electronics, data storage, processing, recording media, catalysis, biotechnology, and pharmacology [18, 19, 20]. Second, advances in film growth methods [9, 21].Third, enhancements in characterization methods [5, 7, 8, 22]. In the context of the current work, antiferromagnetic thin films, which are used in spin valve applications [1, 2, 23, 24, 25, 26, 27, 28], is a challenge area of research. Although the technological importance of the spin valve, few research have been done on the antiferromagnetic thin films due to the inability of conventional methods to spatially determine the microscopic magnetic structure of the antiferromagnetic thin films [29].Recently, this
problem has been partially solved by the use of Xray magnetic linear dichroism spectroscopy [30, 31, 32, 33]. Even though, antiferromagnetic thin films remain an experimental and theoretical challenge. The second important class of quasi two dimensional systems is the
layered magnetic compounds as the rare earth (RE) ions in the family compounds REBa2Cu3O7δ (0 < δ < 1). These rare earth compounds are suggested to be quasitwodimensional systems because their structures consist of the a planes of RE ions each of which lie between two double
copper oxide layers, and the axis is approximately three times as long as he a and b axes [34, 72]. This class of magnetic materials is very interesting because nearly all rare earth ions in such compounds show antiferromagnetic ordering at low temperatures (2K°), and this ordering
phase coexists with the superconducting phase. In the case of ErBa2Cu3O7, for example, neutron scattering technique shows that its magnetic spins are
ordering within the plane (with NeŽel temperature TN ≈ 0.50 K°). In this case, the magnetic spins are aligned ferromagnetically in the b direction and antiferromagnetically in the a direction. This phase is denoted as the dipolar antiferromagnetic phase (AF1 phase).
The third important class of quasitwodimensionalsystems is the magnetic micro or nano particles; where a large number of publications with different geometries have been considered, including regular arrays of magnetic nano particles such as dots, rings, tubes, and wires [43, 44, 51, 52, 53, 54, 55, 56, 57] .
In addition to the basic scientific interest in themagnetic properties of the nanodots, there is evidence that they might be used in the production of new magnetic devices, specially in recording media [60, 61]. Obviously, modern technology demands techniques capable of producing nano meter sized structure over large areas. A good perspective is the use of nano dots nickel that could store terabyte of data in a computer chip just a few centimeters wide [74]. Recent studies on such structures have been carried
out with the aim of determining the stable magnetized state as a function of the geometry of the particles [62, 63]. In particular, the study of highly ordered arrays of magnetic wires with diameters typically in the range of
tens to hundreds of nanometers is a topic of growing interest [64, 65, 66, 67].
The high ordering, together with the magnetic nature of the wires, are fundamental in technological interest, since they can determine the success of patterned media in high density information storage.
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