Pulsed laser deposition (PLD) of high quality nanometers thick (YIG) films have recently allowed to open the field of spintronics and magnonics nanostructured magnetic insulators[1,2]. YIG is a versatile material in term of anisotropy or magnetization as doping and growth induced strain can significantly change those properties. We present here the effect of Bi substitution on Bi:YIG PLD grown films with thicknesses ranging from 10 nm to 40 nm. By using lattice matched substituted GGG substrates (sGGG) it is possible to stabilize for specific growth conditions an out-of plane easy magnetization axis. We present comprehensive structural charcterisation using X-ray diffraction and squid magnetometry that shows the transition from an easy in-plane magnetization direction to an out-of plane magnetization. The effect of Bi doping is to significantly increase the Faraday rotation of the films. Using magneto-optical Kerr microscopy, it is therefore possible to observ the shape and the sizes of the magnetic domains for films thicknesses down to 10 nm. Using the Kooy and Enz model it is possible to extract a domain wall energy of 0.49 erg/cm2.
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 M. Collet et al., Nature communications 7, 10377 (2016).
 C. Kooy and U. Enz, Philips Res. Rep., vol. 15, pp. 7-29(1960)