Journal of Magnetism and Magnetic Materials 237 (2001) 302–308 Coupling between neutron spin states in a proposed new spin directional coupler S.P. Pogossian a, *, H. Le Gall a , J. Ben-Youssef a , A. Menelle b a Laboratoire de Magn ! etisme de Bretagne, UFR Sciences, Universite de Brest, CNRS/UPRESA 6135, UBO, 6, Av. Le Gorgeu, BP: 809 Breast Cedex, 29285 Brest, France b Laboratoire L ! eon Brillouin, CEA-CNRS, CE-Saclay, 91191 Gif-sur-Yvette, France Received 26 June 2001 Abstract A new neutron spin directional coupler in a magnetic multilayer waveguide is proposed. Quantum interference between neutron spin states in the latter structure will take place. The proposed structure has spin switching properties. It is shown that this kind of structures can be realized in magnetic spin-switches. r 2001 Elsevier Science B.V. All rights reserved. PACS: 75.25.+z; 61.12.Ha; 75.70.I; 85.70.Kh Keywords: Neutron waveguide; Directional coupler; Magnetic multilayers; Spin 1. Introduction In the recent past, the neutron de Broglie wave propagation in magnetic thin film structures has aroused lively interest in the nuclear and magnetic scientific communities. Neutrons can be used to obtain useful information concerning the magnetic structure of layered media via the neutron magnetic moment interaction with the magnetiza- tion vector. Namely that is, the polarized neutron reflection can be used as a probe of magnetic multilayer with an arbitrary magnetization profile distribution [1–3]. Neutrons can also be a tool for the investigation of surface magnetism [4–6]. Various interesting applications of neutron optical properties are possible and one can find several in the following Refs. [7,8]. The guided wave propagation is one of them and was recently observed experimentally by several authors [9–12]. Neutron guided propagation in magnetic thin films presents interesting spin selective properties [13,14] and various coupling devices and compo- site waveguide structures were proposed [15,16]. Directional couplers exploit the wave nature of particles to realize transfer of a particle from one guide to another. Neutron directional couplers are closely related to the electron directional couplers of semiconductor physics. In the past, electron, as well as light directional couplers have been realized experimentally [17–22]. The first neutron coupled resonators were realized by Steyerl et al. [23]. To the best of our knowledge, nobody has yet demonstrated a neutron directional coupler *Corresponding author. E-mail address: pogossia@univ-brest.fr (S.P. Pogossian). 0304-8853/01/$ - see front matter r 2001 Elsevier Science B.V. All rights reserved. PII:S0304-8853(01)00509-1