Okuma Ryutaro, Kofu Maiko, Asai Shinichiro, Avdeev Maxim, Koda Akihiro, Okabe Hirotaka, Hiraishi Masatoshi, Takeshita Soshi, Kojima Kenji M, Kadono Ryosuke, Masuda Takatsugu, Nakajima Kenji, Hiroi Zenji
Institute for Solid State Physics, University of Tokyo, Kashiwa, Chiba, Japan.
Okinawa Institute of Science and Technology Graduate University, Onna, Okinawa, Japan.
Nat Commun. 2021 Jul 19;12(1):4382. doi: 10.1038/s41467-021-24636-1.
Dimensionality is a critical factor in determining the properties of solids and is an apparent built-in character of the crystal structure. However, it can be an emergent and tunable property in geometrically frustrated spin systems. Here, we study the spin dynamics of the tetrahedral cluster antiferromagnet, pharmacosiderite, via muon spin resonance and neutron scattering. We find that the spin correlation exhibits a two-dimensional characteristic despite the isotropic connectivity of tetrahedral clusters made of spin 5/2 Fe ions in the three-dimensional cubic crystal, which we ascribe to two-dimensionalisation by geometrical frustration based on spin wave calculations. Moreover, we suggest that even one-dimensionalisation occurs in the decoupled layers, generating low-energy and one-dimensional excitation modes, causing large spin fluctuation in the classical spin system. Pharmacosiderite facilitates studying the emergence of low-dimensionality and manipulating anisotropic responses arising from the dimensionality using an external magnetic field.
维度是决定固体性质的关键因素，也是晶体结构明显的固有特征。然而，在几何阻挫自旋系统中，它可以是一种涌现且可调的性质。在此，我们通过μ子自旋共振和中子散射研究了四面体簇反铁磁体——水羟铁矿的自旋动力学。我们发现，尽管在三维立方晶体中由自旋为5/2的铁离子构成的四面体簇具有各向同性连接性，但自旋关联仍呈现二维特征，我们将此归因于基于自旋波计算的几何阻挫导致的二维化。此外，我们认为在解耦层中甚至会出现一维化，产生低能和一维激发模式，在经典自旋系统中引起大的自旋涨落。水羟铁矿有助于研究低维性的出现，并利用外部磁场操控由维度产生的各向异性响应。
