Thin film signal detection by magnetic resonance force microscopy

Abstract

Magnetic resonance is developed in early 20s century and achieve good works in fields of physics, chem-istry, and biology, needless to say, in fields of medicine and biotechnology. And, this method revolutionized the practice of these fields by providing chemically selective, non-destructive, and locally probing means for the observation of matter from the atomic to the macroscopic scale. The one major weakness of NMR is the low detection sensitivity, which limits its application to bulk samples. Nowadays thin film samples are used in many areas. The bulk and thin film, even though they are composed of same materials, have different characteristics, and it needs to investigate the thin film samples for characterizing. However, except few specific cases, thin film NMR has never been detected by conventional NMR method because of its poor sensitivity. To overcome this shortage of magnetic resonance, Magnetic Resonance Force Microscopy (MRFM) was proposed. It is a com-bined technique of magnetic resonance and scanning probe microscopy(SPM). This technique increased the sensitivity of magnetic resonance extraordinarily. The aim of the works in this article is to investigate thin films by NMR using the high sensitivity of MRFM. For preliminary study, Electron Spin Resonance(ESR) signal from DPPH was observed and investigated at room temperature. Low temperature MRFM was developed for higher signal to noise ratio. In NMR studies, natural line width and spin lattice relaxation time($T_1$) are most important factors for characterizing condensed matter systems. By modifying the MRFM set up, The natural line width and spin lattice relaxation time($T_1$) of general thin film samples were obtained for the first time.