A study of uranium-based multilayers: II. Magnetic properties

SQUID magnetometry and polarized neutron reflectivity (PNR) measurements have been employed to characterize the magnetic properties of U/Fe, U/Co and U/Gd multilayers. The field dependence of the magnetization was measured at 10 K in magnetic fields up to 70 kOe. A reduction in the magnetic moment was found for all systems. Magnetic ‘dead’ layers of ∼15 Å were determined for U/Fe and U/Co samples, indicative of chemically diffuse interfaces. For very thick layers, magnetic moments close to the bulk values were expected. For the U/Gd system, a large reduction in the magnetic moment, constant over a wide range of Gd layer thicknesses, was found (∼4 µB compared with 7.63 µB for the bulk metal). A possible explanation for this behaviour, consistent with observations of the structure of these multilayers, is that the Gd moments are pinned at the boundaries of column-like crystallites within the Gd layers. A study of the effective anisotropy and of a finite-size scaling behaviour of the U/Gd system is also presented. PNR data were collected in a field of 4.4 kOe for U/Fe and U/Co samples (at room temperature) and for U/Gd samples (at 10 K). Model calculations of the reflectivities used inputs extracted from the structural survey carried out on these systems, combined with data from the bulk magnetization measurements.

[1]  G. Lander,et al.  A study of uranium-based multilayers: I. Fabrication and structural characterization , 2007, 0704.3947.

[2]  G. Lander,et al.  Magnetism of uranium/iron multilayers: II. Magnetic properties , 2004 .

[3]  G. Lander,et al.  Magnetism of uranium/iron multilayers: I. Fabrication and characterization , 2004 .

[4]  J. Sousa,et al.  Finite size scaling and universality class in ultrathin films , 2004 .

[5]  K. Mergia,et al.  Magnetic properties of ultra‐thin epitaxial V/Gd bilayers , 2004 .

[6]  J. Glimm,et al.  Surface magnetic moment in α-uranium by density-functional theory , 2003 .

[7]  K. Mergia,et al.  Polarized neutron reflectivity study of a Gd/Cr multilayer , 2002 .

[8]  S. Srinath,et al.  Gadolinium: A helical antiferromagnet or a collinear ferromagnet , 2000 .

[9]  A. Wawro,et al.  Magnetic anisotropy in MBE-grown epitaxial gadolinium ultra-thin films , 2000 .

[10]  Yi Li,et al.  Thickness and magnetic field dependence of the ferromagnetism of ultrathin Gd films in Gd/W multilayers , 1998 .

[11]  Sung-chul Shin,et al.  Interface roughness effects on the surface anisotropy in Co/Pt multilayer films , 1996 .

[12]  P. Donovan,et al.  Interface pinning in gadolinium/molybdenum magnetic multilayers , 1996 .

[13]  P. Donovan,et al.  The structure and magnetization of gadolinium/molybdenum multilayers , 1996 .

[14]  Jiang,et al.  Oscillatory superconducting transition temperature in Nb/Gd multilayers. , 1995, Physical review letters.

[15]  Huang,et al.  Magnetism in the few-monolayers limit: A surface magneto-optic Kerr-effect study of the magnetic behavior of ultrathin films of Co, Ni, and Co-Ni alloys on Cu(100) and Cu(111). , 1994, Physical review. B, Condensed matter.

[16]  R. Stamps,et al.  Magnetic multilayers : spin configurations, excitations and giant magnetoresistance , 1993 .

[17]  M. Farle,et al.  Thickness-dependent Curie temperature of Gd(0001)/W(110) and its dependence on the growth conditions. , 1993, Physical review. B, Condensed matter.

[18]  Pearson,et al.  Asymmetry of the spin reorientation transition in ultrathin Fe films and wedges grown on Ag(100). , 1993, Physical review letters.

[19]  Berger,et al.  Magnetoresistivity and oscillatory interlayer magnetic coupling of sputtered Fe/Nb superlattices. , 1992, Physical review letters.

[20]  C. Chien,et al.  Structural and magnetic properties of Fe/W superlattices , 1991 .

[21]  C. D. England,et al.  Structural and magnetic properties of Ti/Co multilayers , 1990 .

[22]  Kirschner,et al.  Curie temperature of ultrathin films of fcc-cobalt epitaxially grown on atomically flat Cu(100) surfaces. , 1990, Physical review letters.

[23]  P. Bruno.  Magnetic surface anisotropy of cobalt and surface roughness effects within Neel's model , 1988 .

[24]  Cowen,et al.  Finite-size effects in a CuMn spin-glass. , 1987, Physical review letters.

[25]  A. J. Freeman,et al.  Handbook on the Physics and Chemistry of the Actinides , 1985 .

[26]  Kenji Kawaguchi,et al.  Magnetic Properties of Fe-V Multilayered Films with Artificial Superstructures , 1984 .

[27]  J. Ketterson,et al.  The magnetization and Curie temperature of compositionally modulated Cu/Ni films , 1982 .

[28]  M. Farle,et al.  The temperature dependence of magnetic anisotropy in ultra-thin films , 1997 .

[29]  J. Bland,et al.  Ultrathin Magnetic Structures III , 1994 .

[30]  G. D. Parfitt,et al.  Surface Science , 1965, Nature.