Uniaxial anisotropy

Anisotropy of single-axis

Anisotropy, referred to as anisotropy, is a general term for the property of solids having material properties (such as mechanical, electrical, optical, magnetic, thermal parameters, etc.) that vary with the direction of measurement. Single-axis anisotropy is an anisotropy whose material properties (such as mechanical, electrical, optical, magnetic, thermal parameters, etc.) vary along the direction of a certain axis.

In single-axis anisotropy, the physical properties of materials vary with the direction in the plane perpendicular to the single axis, which is mainly divided into three types: uniaxial anisotropy, anisotropy along two orthogonal axes, and cubic anisotropy with three orthogonal axes.

Uniaxial anisotropy refers to an anisotropy state in which material properties are the same in directions perpendicular to the single axis, and the physical properties such as magnetization, electric field, and stress of the materials vary in the direction of the single axis. Material with uniaxial anisotropy is of particular interest in magnetism. Its magnetic properties (hysteresis properties, residual magnetization, saturation magnetization, coercive force, etc.) of materials mainly depend on one external field acting on the material in which the easy axis is unidirectional. Anisotropic materials generally show special electrical and magnetostrictive effects in the easy axis direction.

When a magnetic field is applied to a ferromagnetic material with anisotropy along two perpendicular axes, the materials magnetic body is tiled in an appropriate direction determined by the direction of the magnetic field, showing an axial anisotropy. The magnetization of the material has the characteristic that its direction is fixed according to the direction of the applied magnetic field and changes abruptly with the change of the direction of the magnetic field. This material is called two-fold anisotropy.

Cubic anisotropy refers to an anisotropy with two easy-axis directions, two hard-axis directions, and a neutral axis perpendicular to the easy and hard axes. When the magnetization direction is the same as the easy-axis direction, the energy is the smallest, while when it is the same as the hard-axis direction, the energy is the largest, and it is intermediate when it is in the neutral direction.

Single-axis anisotropy has found many applications due to its distinct material properties. For example, a single-axis type of magnetic read/write head is widely used in hard disk drives and other forms of magnetic storage. Single-axis anisotropy magnetic materials also have application in the field of magnetic sensors as they possess a high level of sensitivity to magnetic fields. Another example of single-axis anisotropy material is magnetorheological fluids. These are used in shock absorber systems where the viscosity of the fluid can be adjusted by the application of an external magnetic field.

In summary, single-axis anisotropy refers to an anisotropy state in which material properties (such as mechanical, electrical, optical, magnetic, thermal parameters, etc.) vary along the direction of a certain axis. Its characteristics are mainly divided into three, unidirectional anisotropy, two orthogonal axes anisotropy, and cubic anisotropy. Single axis anisotropy has found many applications where it is utilized in a variety of areas such as in the fields of magnetic storage and magnetic sensors as well as in shock absorber systems for viscosity adjustment purposes.

Anisotropy refers to the phenomena that the properties of a material show different directional behaviors. Materials which have anisotropicity have distinguished physical or chemical behavior when examined under different orientations. Uniaxial anisotropy is among the most significant types of anisotropic behaviors that is influenced by external stimulus such as temperature, humidity, electric fields, and pressure, etc. It involves a preferential alignment of molecular or crystallographic planes in one specific crystallographic direction. The orientation of the molecular or crystallographic planes depends on the underlying material structure and is affected by external stimuli, such as the application of electric fields or stress. The directional variation of the material characteristic can be deduced and simultaneously captured with a uniaxial stress or couple of electric or magnetic fields. Typically this anisotropic behavior is depicted in terms of a uniaxial anisotropy factor (K1). Uniaxial anisotropic behavior has been studied extensively in many types of materials, such as semiconductors, metals, and dielectrics, in which anisotropy is important in controlling the electronic, thermal, vibrational, optical, and mechanical properties of the material.

Using the electrical effect, the direction of uniaxial anisotropy can be modified by inducing an electric field in uninform directions. The response of any material at a given direction is determined by the dipole moments of the atoms in the material, which depend on the degree of electric polarity of the atoms. By changing the direction of the electric polarity in an atom along a certain direction, the uniaxial anisotropy can be manipulated if the material is monocrystalline. Further, uniaxial anisotropy of an amorphous material can be tuned by applying a longitudinal electric field or a couple of transverse electric fields. The induced electric field changes the orientation of the dipoles and modifies the anisotropy in a novel manner, which determines the direction of uniaxial anisotropy.

Moreover, uniaxial anisotropy has been studied in novel materials, such as graphene, gold nanowires, nanotubes, and carbon nanotubes. It has been discovered that uniaxial anisotropy in graphene can be utilized to construct nanomechanical sensors and to modify the dispersion properties of light. Gold nanowire-based optical switches have also been developed to control the wave propagation direction. Carbon nanotubes, on the other hand, can help to capture heat from a source when arranged in a particular direction, which can be used to generate power. The applications of uniaxial anisotropy correlate strongly with the material structure, and researchers continue to explore further applications.