# FM and AFM magnon dispersion

• A
• jksy
In summary, the DOS in one dimensional AFM and FM magnon dispersion relations can be calculated using the equation DOS(ω) = Σqδ (ω - ωq) where ωq is the magnon energy at a wave vector q and δ is the Dirac delta function. At q=0, the DOS approaches 0 and the spin entropy decreases as there is less energy available for the spins to be in higher energy states.

#### jksy

How calculate the DOS from the one dimensional AFM and FM magnon dispersion relations given in Kittel? What is there limiting form as q -> 0, and how does this affect the spin entropy?

The DOS in one dimensional AFM and FM magnon dispersion relations can be calculated using the equation: DOS(ω) = Σqδ (ω - ωq). In this equation, ωq is the magnon energy at a wave vector q, and δ is the Dirac delta function.At q=0, the limiting form of the DOS is equal to the magnon gap energy. This means that as q -> 0, the DOS approaches 0. This has an effect on spin entropy, since it means that there is less available energy for the spins to be in higher energy states. As a result, spin entropy decreases as q -> 0.

## 1. What is the difference between FM and AFM magnon dispersion?

FM (ferromagnetic) and AFM (antiferromagnetic) magnon dispersion refer to the behavior of spin waves in different types of magnetic materials. In FM materials, the spins of the electrons are aligned in the same direction, while in AFM materials, the spins are aligned in opposite directions. This difference in spin alignment leads to different dispersion patterns for magnons, which are the quanta of spin waves.

## 2. How is magnon dispersion measured in FM and AFM materials?

Magnon dispersion can be measured using techniques such as inelastic neutron scattering or Brillouin light scattering. These methods involve sending a beam of particles or light towards the material and measuring the scattered particles or light to determine the energy and momentum of the magnons.

## 3. What factors influence the shape of the magnon dispersion curve?

The shape of the magnon dispersion curve is influenced by several factors, including the strength of the magnetic interactions in the material, the spin alignment, and the crystal structure. In FM materials, the strength of the exchange interaction between neighboring spins plays a significant role, while in AFM materials, the strength of the superexchange interaction between spins on different sublattices is crucial.

## 4. What is the significance of understanding magnon dispersion in materials?

Understanding magnon dispersion is essential for studying the magnetic properties of materials and developing new technologies such as spintronics. Magnons are the carriers of spin information, and their dispersion can reveal information about the magnetic interactions and ordering in a material. Additionally, the ability to control magnon dispersion could lead to new ways of manipulating and storing information in magnetic materials.

## 5. Can magnon dispersion be modified in materials?

Yes, magnon dispersion can be modified in materials through various methods such as applying an external magnetic field or changing the material's composition. These modifications can alter the strength of the magnetic interactions and change the spin alignment, resulting in changes to the magnon dispersion curve. Manipulating magnon dispersion is an active area of research with potential applications in spin-based devices.