China
Africa
Explore chapters and articles related to this topic
Spin Waves on Spin Structures: Topology, Localization, and Nonreciprocity
Published in Sergej O. Demokritov, Spin Wave Confinement, 2017
Robert L. Stamps, Joo-Von Kim, Felipe Garcia-Sanchez, Pablo Borys, Gianluca Gubbiotti, Yue Li, Robert E. Camley
In the second half of this review, we discuss a possibility for creating a mesoscopic metamaterial analogue of domain wall channeling. The idea in this case is very different and relies upon a new emerging technological concept sometimes referred to as artificial spin ice (ASI). Artificial magnetic spin ice is an arrangement of interacting nanomagnets with emergent collective magnetic properties. A straightforward and well-studied example is square ASI, wherein elements are arranged such that the dipolar interactions result in a type of antiferromagnetic alignment. The single-domain magnetic elements in these structures can spontaneously order into two sublattice arrays of alternating magnetic orientations on a two-dimensional square lattice. Relatively simple alterations of the array geometry can be made to produce other types of ordering or create frustration through competing interactions as occurs in spin glasses.
Magnetic Disorder at the Nanoscale
Published in Klaus D. Sattler, 21st Century Nanoscience – A Handbook, 2020
Nader Yaacoub, Rodaina Sayed Hassan
The no simultaneously satisfaction of different magnetic interactions allows to a certain degree of spin disorder, in this case the magnetic material exhibits a non-collinear spin structure. This is a very large subject, and this behavior may have a different origin. Due to geometrical constraints the system can exhibit a geometrical frustration like triangular or Kagome lattices (Martinez et al. 1994, Nishimoto et al. 2016). In this system the nearest-neighbor interactions are naturally frustrated and demonstrate unusual behavior and could have degenerate ground states (Ramirez et al. 1999). The mismatch between the crystal symmetry and the desired bonding in water, for example, allows to natural frustrated system (Bramwell et al. 2009). Magnetic moments frustration could result also from the competition between exchange and dipole–dipole interactions in natural spin ice (Ramirez et al. 1999). In this general framework, and in order to better understand the nature and the ground state in disordered system, frustrated artificially structures have been studied, like artificial square (Wang et al. 2006) and artificial Kagome spin ice (Qi et al. 2008, Ladak et al. 2010, Morgan et al. 2011, Moeller and Moessner 2009, Rougemaille et al. 2011). Disorder associated with random interactions (random anisotropy, random exchange interaction, etc.) and the competition between them might lead to destruction of long-range order and important change in the magnetic properties. The speromagnetism is an example of the random anisotropy. This behavior was established in finely divided amorphous ferric gel (Coey and Readman 1973a, b, Hurd 1982) for the first time by studying their Mössbauer spectra. The spins are frozen in essentially random orientations because topological frustration, which leads to frustration of the individual superexchange, bonds in amorphous oxide. The speromagnetic material exhibit a zero magnetization due to an isotropic moment distribution. We can cite also the asperomagnetic and sperimagnetic behavior, observed in amorphous systems. In case of A-B binary amorphous alloy, because the competition between the ferromagnetic and antiferromagnetic interactions, a sperimagnetic configuration arises (Coey and Readman 1973a, 1973b, Coey 1993). When the exchange distribution is broad, an intermediate behavior is observed, the asperomagnetism, which is characterized by a non-zero magnetization with a moment distribution pointing in a preferential direction. In general, the spin system is frustrated when one cannot find a configuration of spins to fully satisfy the interactions between every pair of spins.
Helium II phase: superfluid, supersolid, liquid crystal or spin ice?
Published in Molecular Physics, 2022
The experimentally observed microwave response of the He II phase can be clarified only through effect of the spin subsystem because namely the spin degrees of freedom can be responsible for the processes with energies of a few Kelvins, and simultaneously are able to interact effectively with an external electromagnetic field of the microwave diapason. Just the spin subsystem is responsible for electromagnetic activity of such as He II phase macroscopically electro-neutral dielectric medium with extremely low palarisability. Moreover, the regular spin-possessed microwave response is possible only at the presence of spin ordering, but spins are intrinsic property of electrons collectivised and distributed within He II valence bond [248,249]. Electrons are confined in atomic shells, so that the He II phase as an atomic system must be spatially ordered. Certainly, various effects of spin–orbit coupling are possible [250]. It is the nature of the λ-transition which was rightly compared by Shubnikov [1] with Curie transition in ferromagnets. Spin subsystem plays the paramount role for atom-atom interaction in helium, and in this connection the He II phase can be characterised undoubtedly as an evident spin ice.
Super-hierarchical and explanatory analysis of magnetization reversal process using topological data analysis
Published in Science and Technology of Advanced Materials: Methods, 2022
Sotaro Kunii, Alexandre Lira Foggiatto, Chiharu Mitsumata, Masato Kotsugi
The microstructures of magnetic domains are critical in characterizing the functions of various advanced magnetic devices. In the next generation of high-speed and high-density information devices, the reliability of data storage and writing speed processes will be determined by changes in microscopic magnetic domain structures [1–4]. Since 0/1 of bit is recorded as positive/negative magnetization, the precise control of the vortex core in magnetic domain structures is key to controlling the information in the racetrack memory or magnetoresistive random access memory (MRAM) of spintronics devices [5–8]. In addition, the magnetic domain structure in artificial spin ice has attracted significant attention for the realization of quantum computers [9–11]. The topological symmetry of magnetic nanowires causes fluctuations in the stability of magnetic moments, resulting in unique orders such as frustrated magnetism. In the motors of next-generation electric vehicles, understanding the magnetization reversal process is essential to reducing iron losses in electromagnetic steel sheets to improve their power generation efficiency [12–14]. Therefore, magnetic materials have a wide range of applications, such as information devices, quantum computing, and electric vehicles. They are extremely important for realizing a sustainable society [15]. Since these macroscopic magnetic functions are achieved by controlling the microscopic magnetic domain structures and stability of the magnetization reversal process, it is essential to develop an analytical method that can realize a hierarchy in materials and explain the origins of certain functions.