Epitaxial SmCo5 films
The research on Sm-Co thin film magnets in our group is focussed primarily on epitaxial growth and characterization of the anisotropic magnetic properties. Thin films are prepared using pulsed laser deposition on single crystalline MgO substrates with different substrate orientations to obtain different growth textures. On MgO(100) oriented substrates, low deposition temperatures of 350°C, along with low repetition rates of 5 Hz have been sufficient to achieve suitable epitaxial growth of Sm-Co films with two orientations of the easy axis (Figure 1). This epitaxial relation becomes visible in the magnetic hysteresis, when measurements are performed along two non-equivalent in-plane substrate orientations: parallel to the easy axis (black curve) and at 45° to the easy axis (green curve). An increase in the remanence is observed for the 45° orientation, which is in accordance with the Stoner-Wohlfarth model.
The magnetic easy c-axis on MgO(100) lies along two equivalent substrate orientations but for practical application and for the examination of anisotropic magnetization phenomena, a strong uniaxial texture is desirable. This is achieved on MgO(110) single crystal substrates, where due to lower symmetry of the substrate the Cr buffer grows in a (211) orientation and subsequently SmCo has only one unique c-axis orientation with respect to the substrate. At optimised deposition conditions, a continuous buffer morphology can be obtained and Sm-Co grows with the mentioned texture, as shown in Fig. 2. Measurement along the easy axis result in a square shaped hysteresis, with high coercivity of up to 3 T and high saturation magnetization of 0.94 T. The other two perpendicular directions are magnetically hard and show very low remanence and coercivity.
- E. Stilp, F. Freudenberger, M. Seifert, A.K. Patra, S. Menzel, I. Mönch, L. Schultz, V. Neu, Probing the anisotropy constants of SmCo5 and PrCo5 by Hall resistance measurements in pulsed high magnetic fields up to 47 T, J. Magn. Magn. Mater. 234, 1711 (2012).
- A. Singh, V. Neu, S. Fähler, K. Nenkov, L. Schultz, and B. Holzapfel, Relevance of pinning, nucleation, and interaction in nanograined epitaxial hard magnetic SmCo5 films, Phys. Rev. B 79 214401 (2009).
A. Singh, V. Neu, K. Nenkov, S. Fähler, L. Schultz, and B. Holzapfel, Mechanism of coercivity in epitaxial SmCo5 thin films, Phys. Rev. B 77 104443 (2008).
- U. Wolff, A. Singh, L. Schultz, V. Neu, Switching behaviour of patterned SmCo5 thin films investigated by magnetic force microscopy, presented at ICM, Kyoto 2006, J. Magn. Magn. Mater. 310, 2210 (2007)
- A. Singh, V. Neu, R. Tamm, K. Rao, W. Skrotzki, L. Schultz, B. Holzapfel, Pulsed laser deposited epitaxial Sm-Co thin films with uniaxial magnetic texture, J. Appl. Phys. 99, 08E917 (2006)
- A. Singh, V. Neu, R. Tamm, S. Rao, S. Fähler, B. Holzapfel, W. Skrotzki, L. Schultz, Growth of epitaxial SmCo5 films on Cr/MgO(100), Appl. Phys. Lett. 87, 072505 (2005)