Z. Phys. B - Condensed Matter 62, 31-41 (1985) Condensed Zeitsohrift Matter ffir Physik B 9 Springer-Verlag 1985 Effects of Short-Range Magnetic Order on Photoemission and Inverse Photoemission Spectra in Iron R. Clauberg 1, E.M. Haines 2 and R. Feder 3 Institut ffir Festk6rperforschung, Kernforschungsanlage Jfilich GmbH, Federal Republic of Germany Received July 18, 1985 The dependenc of spin-resolved photoemission and inverse photoemission spectra on short-range magnetic order below and above Tc is investigated within a bulk interband transition model. The spectra are calculated in a 2000-atom cluster of bcc-Fe with local exchange field configurations, which are random subject to an assumed spin-correlation function. The model continuously bridges the gap between the '" disorderedqocal-moment picture" (no short-range order) and a "local-band picture" (massive short-range order). Special emphasis is given to the analysis of factors like group velocity and the symmetry of the wave function by investigating special points in the Brillouin zone. Comparison with experimental data reveals a short-range order of at least 4 ~ (corresponding to a nearest-neighbour correlation of about 0.4) near To. I. Introduction The electronic structure of the 3 d transition metals Fe, Co, and Ni and its relation to ferromagnetism has long been a matter of debate. While the overall picture of the ground state properties at zero temper- ature seems to be well understood in terms of the itinerant band model, no general accepted microscop- ic model exists for finite temperatures. General con- sensus has been reached regarding the importance of spin-density fluctuations for ferromagnetism at finite temperatures, i.e., going beyond the simple Stoner model [1] which simply assumes a continuous de- crease in the size of the magnetic moment by ap- proaching the Curie temperature Tc where the mac- 1 Address after August 1, 1985: IBM Z/irich Research Laborato- ry, CH-8803 Rfischlikon, Switzerland 2 Permanent address: Physics and Engineering Laboratory, DSIR, Private Bag, Lower Hutt, New Zealand 3 Permanent address: Theoretische Festk6rperphysik, FBI0, Universit~it Duisburg GH, D-4100 Duisburg, FRG roscopic magnetization is lost. The current contro- versy is mainly about the actual wavelength distribu- tion of the spin-density fluctuations, i.e., the degree of short-range magnetic order, with a "disordered- local-moment picture" (no short-range order) and a "local-band picture" (massive short-range order) as opposite limiting cases [2-4]. Both models are based on the assumption of existing local magnetic mo- ments even above To. The question tackled in this article is: How far can photoemission and inverse photoemission contribute to the solution of the short-range magnetic order problem? For Ni, spin-resolved photoemission data by Hopster et al. [5, 6] were successfully interpreted by Koren- man and Prange with the assumption of massive short-range order [7], but no prediction for the same data is known without short-range order. So it is most desirable to use a theory which is capable of contin- uously bridging the gap between the disordered-local- moment and the local-band limits, thereby revealing