We have measured the nuclear susceptibility of 3He in Grafoil filled with pure liquid 3He over the pressure region between 0.6 and 31.38 bars and at temperatures down to 0.5 mK with a cw NMR method. The nuclear magnetization corresponding to the adsorbed 3He layers on the Grafoil surface shows a strong ferromagnetic tendency with a periodic behavior as a function of liquid pressure. This observation is attributable to the growth of third and fourth solid 3He layers with the liquid pressure increase. The pressure dependence of the Weiss temperature indicates the third layer is completed at 19 bars and the fourth probably at 28 bars. The number of localized spins estimated from the solid magnetization is almost doubled from 0 to 28 bars, being consistent with this scenario.
Nuclear susceptibility of liquid 3 He in Grafoil preplated by a few layers of 4 He has been studied with a cw NMR method at temperatures between 0.7 and 100 mK under various liquid pressures. The 3.5 layers of 4 He preplating suppress the formation of the first three solid 3 He layers, eliminating most of surface magnetization at saturated vapor pressure. However, with increasing liquid pressure, the magnetization obeying a CurieWeiss law gradually grows in the same way as for pure liquid 3 He. This magnetization, induced by pressurization, is attributable to the formation of solid 3 He layer above the preplated 4 He. It shows a strong ferromagnetic tendency, probably due to the intralayer exchange interaction. 3 He atoms bound on the surface of various materials form a unique system to study two-dimensional magnetism. In particular, 3 He films adsorbed on graphite have extensively been studied, owing to the atomically flat surface and large surface area of graphite. 1 The previous investigations on the adsorbed film have revealed that the first and the second atomic layers solidify on the graphite surface, while the upper layers above the second one exist as liquid. 1 The second solid layer displays a spectacular evolution from antiferromagnetism to ferromagnetism as a function of the areal density. The behavior is understood as a consequence of competing multiple spin exchange ͑MSE͒ interactions within the second layer. On the other hand, the surface magnetism for various materials filled with liquid 3 He was investigated in the 1970s and the magnetization was found to show a ferromagnetic tendency with Weiss temperature around 0.5 mK. 2-4 A very recent study on liquid 3 He magnetization in Grafoil has revealed that the third and the fourth layers grow as solid with increasing the liquid pressure. 5 These upper solid layers show a strong ferromagnetic tendency that depends on the liquid pressure. In the above experiment, however, their detailed nature remains unclear because it is obscured by the magnetization of the first and the second solid 3 He layers. Here, we report our extended experiments where the graphite surface is preplated with 4 He to eliminate the influence of the first two layers.The experimental setup is described in our previous work. 5 The substrate used is an exfoliated graphite ͑Grafoil GTY grade 76 m thick͒, 6 which consists of partially aligned microcrystals of graphite ͑platelets͒. Sixty Grafoil sheets ͑8 ϫ 8 mm 2 ͒ with surface area of 6.74 m 2 are put into a sample chamber made of epoxy ͑Stycast 1266͒. The sample chamber is connected through a narrow channel to a sintered powder heat exchanger, the mixture of Ag and Pt powders with a surface area of about 24 m 2 , to make a good thermal contact with the nuclear stage made of copper. The temperature is measured by a 3 He melting curve thermometer ͑MCT͒ and a Pt NMR thermometer, which are mounted on the nuclear stage. NMR measurements were made with a continuous-wave method at a frequency of 696.1 kHz. A static field of 21.5 mT was appli...
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.