MAGNETIC ORDER AT SURFACES

A fascinating set of experimental questions concerns the behavior of magnetic moments at surfaces. It has been suggested both that magnetic order should be suppressed at surfaces, due to lower coordination number, and alternatively that magnetic order should be enhanced through a bandwidth reduction which drives more efficient moment formation. We have addressed some of these issues through studies of magnetic order in coupled two-dimensional Hubbard layers.[1] We find that interplane hybridization decreases local moments and, eventually, drives singlet formation between the sheets and the destruction of long range magnetic order.

We have also addressed the issue of the observation of enhanced short range magnetic correlations at surfaces in spin-polarized photoelectron experiments.[2] Here we find that enhanced exchange constants at a surface can explain observations of jumps in local surface spin-spin correlations at temperatures well above the bulk transition temperature to a fully magnetically ordered phase.

Relevant Publications:

[1.] R.T. Scalettar, J.W. Cannon, D.J. Scalapino, and R.L. Sugar,
"Magnetic and Pairing Correlations in Coupled Hubbard Planes",
Phys. Rev. B50, 13419 (1994).

[2.] F. Zhang, S. Thevuthasan, R.T. Scalettar, R.R.P. Singh, and C.S. Fadley,
"A Monte Carlo Study of Magnetic Order at Ferromagnetic and Antiferromagnetic Surfaces: Implications for Spin-Polarized Photoelectric Diffraction",
Phys. Rev. B51, 12468 (1995).

[1.] R.T. Scalettar, J.W. Cannon, D.J. Scalapino, and R.L. Sugar, "Magnetic and Pairing Correlations in Coupled Hubbard Planes", Phys. Rev. B50, 13419 (1994).
[2.] F. Zhang, S. Thevuthasan, R.T. Scalettar, R.R.P. Singh, and C.S. Fadley, "A Monte Carlo Study of Magnetic Order at Ferromagnetic and Antiferromagnetic Surfaces: Implications for Spin-Polarized Photoelectric Diffraction", Phys. Rev. B51, 12468 (1995).