Questions tagged [magnetism]

For questions about magnetic systems and materials

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24
votes
3answers
255 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 ...
20
votes
1answer
218 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 ...
18
votes
4answers
1k 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? ...
18
votes
3answers
758 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 ...
18
votes
1answer
142 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 ...
17
votes
1answer
86 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
2answers
232 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.
16
votes
1answer
44 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?". ...
15
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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?
14
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1answer
93 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 ...
13
votes
3answers
201 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 ...
13
votes
1answer
341 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 ...
13
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1answer
99 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)?
12
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2answers
445 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 ...
12
votes
2answers
56 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 ...
11
votes
2answers
1k 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
295 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 ...
11
votes
1answer
138 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 ...
11
votes
1answer
106 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 ...
11
votes
0answers
161 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_{...
10
votes
1answer
246 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 ...
10
votes
1answer
84 views

Why does the S squared value have no meaning in Density Functional Theory?

It is not the first time that I stumble upon the affirmation that spin and the $S^2$ value, under DFT, has no "real physical meaning". Why? If that is true, why are we using it all the time ...
10
votes
1answer
117 views

How can I calculate the J value in an antiferromagnetic material?

I am new to DFT, especially in doing DFT for magnetic materials. I recently came across this paper which indicated the calculation of the J value in the case of antiferromagentic materials as per the ...
9
votes
1answer
187 views

How to perform HSEsol in VASP calculations?

I want to perform HSEsol (PBEsol + HSE06) calculation on a material (monolayer) that doesn't have experimental data available. Could you please tell me how to ...
9
votes
2answers
143 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
254 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]...
9
votes
1answer
748 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 ...
9
votes
2answers
220 views

Can we consider SOC in FM materials using QE?

This is a follow-up question to my question posted here. I've been trying to study the effects of spin-orbit coupling (SOC) on the band structure of ferromagnetic (FM) material VSe$_{2}$. The input ...
9
votes
1answer
186 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 ...
9
votes
1answer
136 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-...
8
votes
2answers
171 views

Magnetic Transition Pymatgen Error

I am trying to simulate the change in magnetic moments during a ferromagnetic to antiferromagnetic transition. ...
8
votes
1answer
67 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. ...
8
votes
1answer
50 views

How is SYMPREC used to determine symmetries compatible with local magnetic moments in VASP?

In DFT calculations using vasp, symmetry analysis are performed to determine space group symmetries at first, if symmetrization is turned on, such as ISYM = 2. When magmoms are set in INCAR, ...
8
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0answers
72 views

Band unfolding for magnetic systems [closed]

I'm trying to study the electronic structure of a 1D antiferromagnetic (in which the spin is associated with copper atoms) system, via spin-polarized calculations. The unit cell dimensions are ...
7
votes
1answer
125 views

How to study a new material without any experimental data about it?

My question is a little bit general. I want to study a 2D monolayer material which hasn't any experimental data available, just some first principles DFT works using PBE, LDA and HSE06 (for band ...
7
votes
3answers
553 views

How to determine the value of the difference (U-J) in "Dudarev's approach" for GGA+U calculation using the VASP?

I want to conduct GGA+U calculations using Duradev's approach in VASP code on a ...
7
votes
1answer
101 views

What measured quantity can be associated to the value of the J parameter in the Heisenberg/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 Heisenberg/Ising hamiltonians? Here J is the ...
7
votes
1answer
87 views

Will there be a difference between GGA and GGA+$U$ for material with Sc element involved?

I have a material that contains the transition metal element Sc [3$d$1], and I want to know your opinions if there will be a difference between GGA and GGA+$U$ calculation. Knowing that the other ...
6
votes
1answer
222 views

How is the material $\ce{\alpha-NaMnO2}$ pronounced?

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 ...
6
votes
1answer
134 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 ...
6
votes
1answer
41 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 ...
6
votes
1answer
138 views

Is it possible to calculate/estimate the value of the J parameter to be used in the Heisenberg/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}...
6
votes
0answers
28 views

How to change the magnetization direction in Quantum ESPRESSO?

I have a magnetic crystal system. I want to calculate the total energy of the system if the magnetization direction is aligned in different directions such as [110], [010]. By default Quantum ESPRESSO ...
6
votes
0answers
52 views

Handling multiple self-consistent solutions with DFT+U

It is well-established that within the DFT+U framework, one can achieve several self-consistent solutions with greatly varying energies for the same exact magnetic ordering. In 2010, Meredig et al. ...
6
votes
0answers
27 views

Is it possible to calculate the variation of magnetization M(T) for a diluted magnetic semiconductor?

Is there any simulation program (for example a DFT package) to determine the variation of magnetization M(T) for dilute magnetic semiconductors or doped semiconductors with different concentrations of ...
5
votes
1answer
62 views

How to make ferro, feri and antiferro magnetic structure for QE

I have below &SYSTME information from my input file ...
5
votes
1answer
43 views

Which one should be investigated first? dynamic stability or magnetic stability?

I would like to investigate the stability of $\ce{VI_3}$ monolayer, but I am confused about whether I start directly by performing Phonon spectrum calculation, or I should first investigate the ...
5
votes
1answer
39 views

Are these settings for HSEsol accurate enough?

I have conducted HSEsol relaxation on a monolayer unit cell of 3 atoms using VASP, with the settings below : ...
5
votes
0answers
23 views

Modeling magnetic field of permanent magnet - where to start?

I would like to model magnetic field of a permanent magnet like this one magnet . Ideally, I would like to do it python or any other language. I would like to start with some simple geometry and some ...
5
votes
0answers
35 views

What are Crystal Electric Field Parameters?

What does the following notation mean? $$A_{20}\left<r^2\right> = -100 \mathrm{K}$$ Where $A_{20}$ is termed a Crystal Electric Field Parameter. I often see this notation when reading papers on ...