Force-detected high-frequency electron spin resonance spectroscopy using magnet-mounted nanomembrane: Robust detection of thermal magnetization modulation

Abstract

In this study, we report a conceptually novel broadband high-frequency electron spin resonance (HFESR) spectroscopic technique. In contrast to the ordinary force-detected ESR technique, which detects the magnetization change due to the saturation effect, this method measures the magnetization change due to the change of the sample temperature at resonance. To demonstrate its principle, we developed a silicon nitride nanomembrane-based force-detected ESR spectrometer, which can be stably operated even at high magnetic fields. Test measurements were performed for samples with different spin relaxation times. We succeeded in obtaining a seamless ESR spectrum in magnetic fields of 15 T and frequencies of 636 GHz without significant spectral distortion. A high spin sensitivity of 10 12 spins/G·s was obtained, which was independent of the spin relaxation time. These results show that this technique can be used as a practical method in research fields where the HFESR technique is applicable.

Spin Detection via Parametric Frequency Conversion in a Membrane Resonator

“…Silicon nitride membranes are attractive transducers for spin detection instruments [25][26][27][28]. Their large surface allows simple placement of samples, and their high spring constants ensure low displacement drift and bending even in the proximity of a scanning tip.…”

Force detection of high-frequency electron spin resonance near room temperature using high-power millimeter-wave source gyrotron

“…As previously mentioned, although the detection of DM th z is very effective at low temperatures, the sensitivity drastically decreased as T increased. 9 Considering the temperature dependence of dM 0 =dT ð/ T À2 Þ and C, DM th z at T ¼ 50 K is expected to be less than that at T ¼ 10 K by two orders and even lower at 280 K. On the other hand, jDM Bloch z =M 0 j, which was very small with a low power source, was enhanced by the large B 1 value of the gyrotron. Because c 2 B 2 1 T 1 T 2 for DPPH is an order of unity even at room temperature, DM Bloch z exhibits a similar temperature dependence on M 0 , which obeys the Curie law M 0 / T À1 .…”

“…In our previous study, we achieved a sensitivity as high as 10 12 spins/G at 1.6 K using a silicon nitride nanomembrane. 9 This technique achieved precise broadband spectroscopy of submillimeter-sized samples and microliter solution samples. 10 However, the ESR signal becomes smaller as the temperature increases, which hinders the practical application of this method.…”

“…The other mechanism is much simpler and is due to heating by ESR. 9 The energy absorbed by ESR is used to increase the sample temperature in the spin-lattice relaxation process. By irradiating the slowly amplitude-modulated millimeter wave, M 0 ðTÞ can be modulated while maintaining thermal equilibrium.…”

Force detection of high-frequency electron paramagnetic resonance spectroscopy of microliter solution sample

“…In this study, EPR signals were detected as a field gradient force acting between a sample and a gradient magnet. 13 A tiny drop of Stycast1266 (as a glue) was placed at the center of the SiN x nanomembrane using a micro-injection pipette, and then, a strontium hexaferrite (SrFe 12 O 19 ) sphere with a 40-lm diameter was mounted as a gradient magnet. After the gradient magnet was mounted, the eigenfrequency of the membrane decreased down to 1-10 kHz.…”