Magnetic Anisotropy at Nanoscale

Institute of Physics, Polish Academy of Sciences, Al. Lotników 32/46, 02-668 Warszawa, Poland

Marek Gutowski

Given is the model for unusual magnetic anisotropy observed in thin magnetic layers. Assuming that the surface is rippled (what is often observed), we obtain new formula: the magnetic anisotropy energy is proportional to the absolute value of cos(x) rather than to the series of even powers of cos(x). Here "x" is the angle between easy in-plane axis and the direction of external field. This paper has been triggered by experimental observation of the effect predicted few years ago by the current author.

Nanoscale objects often behave differently than their "normal-sized” counterparts. Sometimes it is enough to be small in just one direction to exhibit unusual features. One example of such a phenomenon is a very specific in-plane magnetic anisotropy observed sometimes in very thin layers of various materials. Here we recall a peculiar form of the free energy functional nicely describing the experimental findings but completely irrelevant and thus never observed in larger objects.