RESUMO
We obtained the NMR spectrum and the spin-lattice relaxation time (T1) for thin film samples by magnetic resonance force microscopy (MRFM). The samples were CaF2 thin films which were 50 nm and 150 nm thick. T1 was measured at 18 K using a cyclic adiabatic inversion method at a fixed frequency. A comparison of the bulk and two thin films showed that T1 becomes shorter as the film thickness decreases. To make the comparison as accurate as possible, all three samples were loaded onto different beams of a multi-cantilever array and measured in the same experimental environment.
RESUMO
Nuclear magnetic resonance (NMR) is a fundamental research tool that is widely used in many fields. Despite its powerful applications, unfortunately the low sensitivity of conventional NMR makes it difficult to study thin film or nano-sized samples. In this work, we report the first NMR spectrum obtained from general thin films by using magnetic resonance force microscopy (MRFM). To minimize the amount of imaging information inevitably mixed into the signal when a gradient field is used, we adopted a large magnet with a flat end with a diameter of 336 µm that generates a homogeneous field on the sample plane and a field gradient in a direction perpendicular to the plane. Cyclic adiabatic inversion was used in conjunction with periodic phase inversion of the frequency shift to maximize the SNR. In this way, we obtained the (19)F NMR spectrum for a 34 nm-thick CaF2 thin film.
RESUMO
The technique of magnetic resonance force microscopy (MRFM) is proposed with the purpose to enhance the sensitivity of the inductively detected conventional magnetic resonance technique. The IBM MRFM group demonstrated magnetic resonance imaging (MRI) to the nanoscale level by using MRFM. The spatial resolution of the inductive method is on the order of a few micrometers. In this paper, we introduce an MRFM probe equipped with a charge coupled device (CCD) camera. We show that this CCD camera is very helpful to correct the optical fiber-to-cantilever and magnet-to-sample alignments which can be the determinant of success or failure in an MRFM experiment. Also, this camera enables us to monitor an experimental setup inside a vacuum chamber of P = 10(-5) mbar in real-time. Then, we verified the usefulness of the CCD camera through an electron spin resonance experiment on a diphenylpicrylhydrazyl (DPPH) sample. We also discuss the extensibility of the CCD camera for low temperature experiments, creating an atmosphere in which MRFM can flourish truly to its full potential in the field of nanotechnology.
