Questions tagged [magnetism]
For questions about magnetic systems and materials
34
questions
5
votes
1answer
50 views
How can I properly represent paramagnetic materials in DFT calculations?
I have seen specific ways of constructing input files for
Anti-ferromagnetic materials
Ferromagnetic materials.
How can I represent a paramagnetic material in plane wave DFT codes like Quantum ...
11
votes
1answer
205 views
Are different eigensolvers consistent within VASP (Algo=Normal vs Fast)
I tried to relax a 4x4x1 supercell of ferromagnetic monolayer material using the default settings (ALGO = Normal) but it didn't converge. So, I switched to ...
9
votes
0answers
45 views
Formulate the Model Quantum Spin Hamiltonian for low dimensional (1D or 2D ) magnetic materials
Recently I have started studying the properties of low dimensional magnetic materials by solving the MODEL QUANTUM SPIN HAMILTONIAN.
I am finding difficulties in formulating the model quantum spin ...
9
votes
1answer
119 views
PT-symmetry leading to spin-degenerate band structures
I am trying to understand the fundamental physics of a kind of problem. I will introduce a specific example and then list some of the broader qualms I hold. I have observed many band structures, be it ...
12
votes
2answers
189 views
Getting different total magnetic moment in 'scf' and 'vc-relax' calculations in Quantum ESPRESSO
I am performing a spin polarized DFT calculations in Quantum Espresso on a Co2MnSi ferromagnetic crystal. For this I have performed these steps:
1) Performed ...
13
votes
1answer
199 views
Software for Exact Diagonalization of quantum spin Hamiltonians in 1D and 2D
I'm looking for software (which can also run in parallel) for Exact Diagonalization of Quantum Spin Hamiltonians in 1D and 2D (e.g. Heisenberg Model) consisting of a large number of spin sites.
There ...
18
votes
3answers
562 views
Ising model: How can I spot the critical point?
Consider a zero-field Ising model with $N$ spins and periodic boundary conditions, with the Hamiltonian given by:
$$H = -K \sum _{(ij)} s_i s_j\tag{1}$$
in 1D and 2D, where $K = \frac{J}{k_BT}$, where ...
14
votes
3answers
628 views
Is it possible to calculate the Curie temperature for magnetic systems?
Using DFT calculations we can know the electronic and magnetic property of the system at 0 K. I am wondering if there is any computational method to know the curie temperature of magnetic materials? ...
9
votes
1answer
92 views
Is the “Final Magnetic moment” in the materials project repository same as the “total magnetization” value in Quantum ESPRESSO output files?
I'm quite new to spin-polarized DFT and have been trying to study $BaVSe_{3}$ which is ferromagnetic (with a Final Magnetic Moment of 0.052 Bohr Mag) as per the Materials Project repository [picture 1]...
7
votes
1answer
34 views
How can I assign spins to an non-planar Anti-Ferro Magnetic system (CoO in this case)?
I have been working with an anti-ferromagnetic material Cobalt Oxide. And in the image given below the blue spheres are Co ions. The blue spheres form a tetrahedron shape.
And I've assigned the spin ...
13
votes
2answers
118 views
Are there any codes to study magnetic materials?
I have used a few codes for studying magnetic materials (specifically core-shell nanoparticles with an AFM shell and an FM core). These are:
Vampire: For the calculation of curie temperature via ...
8
votes
0answers
92 views
Orbital magnetization in periodic solids
The orbital magnetization in periodic solids has been nicely described by the so-called modern theory of magnetization [1,2,3,4].
$$\tag{1}
\mathcal{M}_{orb} = -\frac{1}{2} \Im \sum_{n,\mathbf{k}} f_{...
9
votes
1answer
76 views
How to calculate the exchange matrix of a bilayer magentic system?
I have been using the Vampire atomistic simulation software for a while and it has a useful simulation for predicting the curie temperature. But in order to do that I need the exchange matrix of Co-...
10
votes
2answers
84 views
How to visualize MuMax3 shapes?
I'm new to micromagnetics and the finite difference method. The mumax3 software lets you create a variety of geometric shapes. I would like to create a core-shell particle to study magneto-electric ...
9
votes
1answer
59 views
How to predict new Half Metallic materials with higher degree of spin polarization?
Using DFT calculations, how one can predict the new half metallic materials with higher degree of spin polarization. I want to know the steps which have to be followed in prediction of new materials. ...
10
votes
1answer
169 views
How to do spin polarization calculations using Quantum ESPRESSO?
I am currently new to DFT calculations in Quantum ESPRESSO. Though, I have read some research papers for determining spin polarization and Half-metallicity in certain Heusler alloys. These research ...
11
votes
1answer
118 views
Predicting magnetic moment of a metal complex computationally
Recently, for entrance exams, I have been dealing with a lot of weird compounds. One of them is $\ce{K3[Mn(CN)6]}$.
The objective was to predict the magnetic moment of the above complex.
I predict ...
12
votes
2answers
485 views
When should spin polarized calculations be done?
Should the presence of a d block element in the unit cell mandate the need for performing spin-polarized calculations? I wanted to find out the DOS, PDOS, and the band structure. I'm new to DFT and I'...
11
votes
1answer
115 views
How to automatically plot atomic structures with magnetic moments?
I work with magnetic materials and I haven't found a way to automatically plot structures with their corresponding magnetic moments. For this specific project I am using VASP. I am trying to plot ...
11
votes
1answer
68 views
Spin density in systems with non-collinear magnetism using VASP
I have recently been working with non-collinear antiferromagnetic systems. I understand that, in order to obtain spin density, one must obtain the electron density in one configuration of spin and ...
15
votes
3answers
1k views
Magnetism and Topology
Can magnetism and topological insulating behavior coexist in a material? If yes, can someone refer to a recent work?
6
votes
1answer
70 views
What measured quantity can be associated to the value of the J parameter in the Heisengerg/Ising hamiltonians?
This question is related to other one here in the MatterModelingSE:
Is it possible to calculate/estimate the value of the J parameter to be used in the Heisengerg/Ising hamiltonians?
Here J is the ...
6
votes
0answers
82 views
Is it possible to calculate/estimate the value of the J parameter to be used in the Heisengerg/Ising hamiltonians?
Studying magnetic systems, two frequently used approximations are the Heisenberg and Ising models (a discussion about these approximations can be read here):
\begin{equation}
\tag{Heisenberg}
\hat{H}...
15
votes
1answer
83 views
How accurately are magnetic effects treated in *ab initio* methods?
I am a condensed matter theorist and I mostly use quantum Monte Carlo methods. I use models like the Heisenberg model, an represent an extreme simplification of real materials to just localized spin ...
5
votes
1answer
159 views
How is the material $\ce{\alpha-NaMnO2}$ pronounced? [closed]
I am a theoretical physicist, so I am not very familiar with chemical names. The material I am interested in is $\ce{\alpha-NaMnO2}$. Would that be pronounced alpha sodium manganese dioxide? Is it ...
12
votes
1answer
231 views
Is Heisenberg model or in its simplier form Ising model a good approximation to study magnetic systems?
Heisenberg model
$$\hat{H}=-\sum_{\langle i j\rangle}J\hat{S}_i\hat{S}_j$$
And in its simplified version, the Ising model
$$\hat{H}=-\sum_{\langle ij\rangle}J\hat{S}_i^z\hat{S}_j^z$$
are widely ...
24
votes
3answers
178 views
What are examples of materials that closely correspond to the Heisenberg model?
I use the antiferromagnetic Heisenberg model all the time:
$ H = J \sum \limits_{\langle i,j \rangle} \vec S_i \cdot \vec S_j$
What are some examples of materials that are well-described by this ...
12
votes
2answers
49 views
How does magnetic anisotropy cause stable long range magnetic ordering in quasi-one-dimensional solids?
According to Mermin-Wagner theorem ferro/antiferromagnetic ordering cannot occur in ideal one dimensional systems. However there exists quasi-one-dimensional ferromagnetic materials attributing its ...
17
votes
1answer
42 views
Does the thermal evolution of molecular structures critically affect the validity of the calculated magnetic anisotropy?
This is a particular aspect I'm interested in, from the more generic question
"Does the thermal evolution of chemical structures critically affect the validity of the calculated physical properties?". ...
16
votes
2answers
176 views
Is there any good review paper on the density matrix renormalization group (DMRG) method?
I would appreciate if someone could recommend me good review literature on the density matrix renormalization group (DMRG) method, especially for magnetic systems.
19
votes
1answer
186 views
Calculation of the relative energies in a Spin Crossover material
Spin Crossover (SCO) complexes are a particular type of molecular entities which are usually formed by a metal ion (general $\ce{Fe(II)}$ or $\ce{Co(III)}$) complexed by several ligands with donor N ...
13
votes
1answer
94 views
How to model phase transitions at critical regions in a magnetic system?
Is there any first principle method available to study phase transitions at the critical region for ferromagnetism (FM) or antiferromagnetism (AFM)?
17
votes
1answer
75 views
Best partial atomic charges estimate for crystal field purposes?
The estimates for partial atomic charges start with the very simple Mulliken analysis, which we all study in class, but which is known to be very limited. Beyond this, there is a range of ...
16
votes
1answer
89 views
How to evaluate spin exchange parameters of a magnetic material using DFT?
I think we have to calculate total energies using different FM, AFM configurations and solve a set of linear equations. How to arrive at the set of equations for any given structure?
An example from ...
