| The lattice-constant of a solid state material is certainly a key parameter in determining its physical and chemical properties. A well controlled manipulation of lattice constant has always been a dream to modulate the properties of materials. As a key intrinsic parameter of matter, magnetism is also related to lattice constant. Recently, the success of introducing magnetism into electronics, e.g. giant magnetoresistance effect, has waken the enthusiasm on magnetism, especially in low dimension. Most efforts are focused on spintronics and the relationship between structure and magnetism. This thesis work contains several attracted topics on the relation between structure and magnetism, i.e. realization in experiment of manipulating continuously the lattice constant and chemistry, the magnetism of fcc-Fe and bcc-Ni in metastable structure phase, and the unusual properties of directly magnetic coupled trilayer system.(1) We have developed a novel technique that enables to tune artificially the surface lattice constants ("lattice-constant wedge") as well as the surface compositions ("composition wedge") of epitaxial films. This work suggests the possibility of physical and chemical properties of a surface or thin film by fine-tuning its electronic structure.(2) We applied the lattice-constant wedge and composition wedge technique to ul-trathin Fe firms on Cu(001), one of the most important yet still controversial nanomag-netic systems. We found that spin density wave is indeed the magnetic ground state of fcc-Fe, which is quite robust against lattice expansion and Au concentration on the surface.(3) The magnetic coupling between c(2×2) Mn and a Ni film in Mn/Ni/Cu(100) is manipulated by oxygen absorption on the Mn surface. The Mn-Ni magnetic coupling is ferromagnetic for as grown film, but can be switched to antiferromagnetic after a chemisorption of 15 Langmuir of oxygen on Mn. Strikingly the Curie temperature (Tc) of Mn/Ni film before and after the oxygen absorption is lower than that of the bare Ni film, whereas the opposite result would be generally expected. Monte Carlo simulations show that the coupling between Mn atoms is antiferromagnetic, rather than the observed parallel alignment. In addition, such c(2×2) Mn overlayer reduces the spin reorientation transition thickness in Ni/Cu(001).(4) The body-centered-cubic (bcc) phase of Ni, which does not exist in nature, has been achieved as a thin film on GaAs(001). The bcc Ni is ferromagnetic with a Curietemperature of 456 K and possesses a magnetic moment of 0.52 ± 0.08 μB/atom. The cubic magnetocrystalline anisotropy of bcc-Ni is determined to be +4.0×105 erg·cm-3, as opposed to -5.7×104 erg·cm-3 for the naturally occurring face-centered-cubic (fcc) Ni. This sharp contrast in the magnetic anisotropy is attributed to the different electronic band structures between bcc-Ni and fcc-Ni, which are determined using angle resolved photoemission with synchrotron radiation.
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