Spin polarized photoemission studies of the Gd(0001) surface

Fedorov, A. V.; Valla, T.; Huang, D. J.; Reisfeld, G.; Loeb, F.; Liu, F.; Johnson, P. D.

doi:10.1016/s0368-2048(98)00093-0

Cited by 17 publications

(9 citation statements)

References 19 publications

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“…This indicates that the magnetization vanishes near T Cb for both surface and bulk [18]. Spin polarization measurements [19] for out-of-plane magnetization at T $ T Cb rule out the possibility of canted magnetic moments at these temperatures. A more rapid decrease of the surface spin polarization compared to the bulk is consistent with the observations on other ferromagnetic systems [3][4][5], and also with a recent investigation on Gd [18].…”

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confidence: 89%

Novel Sb Induced Reconstruction of the (113) Surface of Ge

et al. 2002

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The temperature dependence of the rare-earth valence bands has been regarded as a realization of the Stoner behavior. The exchange splitting of the electronic states appears to scale as the magnetic order parameter for T , T C and to vanish at T T C . We report here a spin-resolved photoemission study on the evolution of Gd bulk bands for 0.5 # T ͞T C # 1. The spin-polarized spectral line shapes display a complex temperature dependence, which clearly contrasts with the interpretation of previous experimental results. The spin-resolved photoemission data demonstrate the inadequacy of the Stoner model to the description of magnetism in rare earths. DOI: 10.1103/PhysRevLett.88.167205 PACS numbers: 75.70.Ak, 75.25. +z, 79.60.Bm Understanding the relation between electronic and magnetic properties at finite temperatures is a central question for many branches of solid state physics. While the electronic theory accurately accounts for the ground state properties of magnetic materials, it meets only limited success in describing their finite temperature behavior, such as the magnetic phase transitions, the corresponding ordering temperatures, and critical parameters.Two simple models are usually considered to schematically describe the finite temperature behavior of the electronic structure, depending on the degree of the electron localization. The Stoner model [1] predicts that the exchange splitting of delocalized states parallels the temperature dependence of the magnetization. In this case, the exchange-split electronic subbands gradually merge together and become degenerate at the Curie temperature, T C . The spin-mixing model [2], on the other hand, describes strongly localized systems where thermal fluctuations of the local magnetic moment directions reduce the magnetization, but leave the magnitude of the local moments and the local electronic structure unchanged. Thus, the exchange splitting of the electronic states does not vary according to this model, while the characteristic spin polarization of the states is gradually lost on approaching T C .Several experimental studies have examined the finite temperature magnetism in the elemental ferromagnets. The itinerant 3d-transition metals (Fe, Co, and Ni) show an intermediate behavior. The complexity of the temperature dependent effects on the electronic structure in these systems defies any simple description [3][4][5]. Rare earths, on the other hand, provide a different and apparently simpler scenario. The magnetic moment in these systems primarily originates from the unfilled 4f subshell, which displays a simple spin-mixing behavior due to its atomiclike character. The magnetic coupling between the 4f moments occurs via the highly delocalized (5d6s)-valence states [6]. Various investigations by spin-integrated photoemission spectroscopy (PES) and inverse photoemission spectroscopy (IPES) report that the exchange splitting of the bulk valence bands vanishes at T C [7][8][9][10][11]. These experimental results have been interpreted as a first evidence for t...

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Novel Sb Induced Reconstruction of the (113) Surface of Ge

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“…Further we show that the disappearance of magnetism with increasing temperature is a roughly equal mixture of a (Stoner-like) decrease of spin splitting of conduction bands and an increase of opposite-spin components arising from electron-magnon renormalization. A preliminary report of some aspects of this work has been given elsewhere [4].…”

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Spin-resolved photoemission study of photohole lifetimes in ferromagnetic gadolinium

et al. 2002

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High resolution spin-resolved photoemission is used to probe the properties of a Gd(0001) surface state. The state shows both a spin-mixing behavior reflecting the exchange of magnons with the local moments and a reduction of the exchange splitting with increasing temperature. The surface state polarization at low T suggests that the surface layer has an enhanced T c of 365K or greater. Measurements of the photoemission linewidths show that at low temperatures, the lifetime of a majority spin photohole is predominantly limited by electron-phonon scattering and that of a minority spin photohole by electron-magnon scattering. Since similar behavior may be expected for bulk states close to the Fermi level, the transport properties of this material will also be determined by different decay mechanisms in the two channels.

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“…Because of their familiarity and enormous effectiveness, SDA's are now usually used to perform the energy and angle analysis in a spin-ARPES instrument. 105,106,107,108 As shown in the figure and discussed in section 2.7.1, a multichannel PSD can be used in regular ARPES to detect a given count rate in over 10 4 separate channels simultaneously. This allows ARPES data to be taken as 2D slices as depicted to the right of the figure.…”

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A New Spin on Photoemission Spectroscopy

Jozwiak

2008

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Professor Alessandra Lanzara, ChairThe electronic spin degree of freedom is of general fundamental importance to all matter.Understanding its complex roles and behavior in the solid state, particularly in highly correlated and magnetic materials, has grown increasingly desirable as technology demands advanced devices and materials based on ever stricter comprehension and control of the electron spin. However, direct and efficient spin dependent probes of electronic structure are currently lacking.Angle Resolved Photoemission Spectroscopy (ARPES) has become one of the most successful experimental tools for elucidating solid state electronic structures, bolstered by continual breakthroughs in efficient instrumentation. In contrast, spin-resolved photoemission spectroscopy has lagged behind due to a lack of similar instrumental advances. The power of photoemission spectroscopy and the pertinence of electronic spin in the current research climate combine to make breakthroughs in Spin and Angle Resolved Photoemission Spectroscopy (SARPES) a high priority .This thesis details the development of a unique instrument for efficient SARPES and represents a radical departure from conventional methods. A custom designed spin polarimeter based on low energy exchange scattering is developed, with projected efficiency gains of two orders of magnitude over current state-of-the-art polarimeters. For energy analysis, the 1 popular hemispherical analyzer is eschewed for a custom Time-of-Flight (TOF) analyzer offering an additional order of magnitude gain in efficiency. The combined instrument signifies the breakthrough needed to perform the high resolution SARPES experiments necessary for untangling the complex spin-dependent electronic structures central to today's condensed matter physics.

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Spin polarized photoemission studies of the Gd(0001) surface

Cited by 17 publications

References 19 publications

Novel Sb Induced Reconstruction of the (113) Surface of Ge

Novel Sb Induced Reconstruction of the (113) Surface of Ge

Spin-resolved photoemission study of photohole lifetimes in ferromagnetic gadolinium

A New Spin on Photoemission Spectroscopy

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