What is Ferromagnetic: Definition and 75 Discussions

Ferromagnetism is the basic mechanism by which certain materials (such as iron) form permanent magnets, or are attracted to magnets. In physics, several different types of magnetism are distinguished. Ferromagnetism (along with the similar effect ferrimagnetism) is the strongest type and is responsible for the common phenomenon of magnetism in magnets encountered in everyday life. Substances respond weakly to magnetic fields with three other types of magnetism—paramagnetism, diamagnetism, and antiferromagnetism—but the forces are usually so weak that they can be detected only by sensitive instruments in a laboratory. An everyday example of ferromagnetism is a refrigerator magnet used to hold notes on a refrigerator door. The attraction between a magnet and ferromagnetic material is "the quality of magnetism first apparent to the ancient world, and to us today".Permanent magnets (materials that can be magnetized by an external magnetic field and remain magnetized after the external field is removed) are either ferromagnetic or ferrimagnetic, as are the materials that are noticeably attracted to them. Only a few substances are ferromagnetic. The common ones are iron, cobalt, nickel and most of their alloys, and some compounds of rare earth metals.
Ferromagnetism is very important in industry and modern technology, and is the basis for many electrical and electromechanical devices such as electromagnets, electric motors, generators, transformers, and magnetic storage such as tape recorders, and hard disks, and nondestructive testing of ferrous materials.
Ferromagnetic materials can be divided into magnetically "soft" materials like annealed iron, which can be magnetized but do not tend to stay magnetized, and magnetically "hard" materials, which do. Permanent magnets are made from "hard" ferromagnetic materials such as alnico, and ferrimagnetic materials such as ferrite that are subjected to special processing in a strong magnetic field during manufacture to align their internal microcrystalline structure, making them very hard to demagnetize. To demagnetize a saturated magnet, a certain magnetic field must be applied, and this threshold depends on coercivity of the respective material. "Hard" materials have high coercivity, whereas "soft" materials have low coercivity. The overall strength of a magnet is measured by its magnetic moment or, alternatively, the total magnetic flux it produces. The local strength of magnetism in a material is measured by its magnetization.

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  1. abdulbadii

    Stainless steel as ferromagnetic or non/paramagnetic

    Why is this stainless steel ferromagnetic while that one is non/paramagnetic, how's each proportion of them and what's its key difference that'd determines such the distinction?
  2. alukhm

    Wood/Glass/Metal Magnet Inside a Shell containing Ferromagnetic Metal

    Hello all! I have a earring project with magnets involved but no magnet expert involved :( Here are a few stupid questions I hope someone can help us with! BACKGROUND: We are designing magnetic earrings. The earrings are meant to clamp the ear with 3 different levels of pressure. The magnetic...
  3. L

    Magnetization of ferromagnetic material

    I have thought about the following ##\oint \vec{H}\cdot d\vec{l}=0\Leftrightarrow H_{int}(D-h)+H_{ext}h=0\Leftrightarrow (\frac{B}{\mu_0}-M)(D-h)+\frac{B}{\mu_0}h=0\Leftrightarrow M=\frac{D}{D-h}\frac{B}{\mu_0}## but (supposing what I have done is correct) I don't understand which value of ##B##...
  4. abdulbadii

    Magnetizing a ferromagnetic material

    How do we magnetize a ferromagnetic material the best, easiest way, e.g., can we just let it sit around strong magnets in a particular position?
  5. J

    I Why are there not more ferromagnetic Materials?

    Hellooo I have another questions about that fact that we have only a few solids that are ferromagnetic. In ferromagnetics i also read a few time ago it is important to consider 2 things about the reason why there is no magnetizaion. And i don't really understand both reasons, so i hope you can...
  6. CharlieCW

    Force of a magnetized cylinder on a ferromagnetic surface

    Homework Statement A long straight cylinder with radius ##a## and length ##L## has an uniform magnetization ##M## along its axis. (a) Show that when its flat extreme is placed on a flat surface with infinite permeability (i.e. a ferromagnet), it adheres with a force equal to: $$F=8\pi a^2 L...
  7. sergiokapone

    Magnet's force on a metal ball

    As one know, the force on mangnetic dipole in magnetic field is $$ \vec F = (\vec p_m\cdot \nabla) \vec B_0$$, where B_0 -- external field. Let consider a some magnetic matherial with permeability \mu. The magnetization of matherial is $$M = (\mu - 1) H$$ (in SI units) and by deffinition $$M =...
  8. Charles Link

    Susceptibility of Ferromagnetic materials

    A complete table of the ac susceptibility ## \chi_m ## of various ferromagnetic materials, where ## M=\chi_m H ##, is something that I have had trouble finding in a google of ferromagnetic materials. In what I have been able to come up with to date, there is quite a spread in the values of...
  9. G

    Do ferromagnetic materials do "spatial averaging"?

    Hi Everyone - I have a classical E&M physics problem that I've been tearing my hair out over. It relates to how ferromagnetic materials boost the field strength of a non-uniform magnetic field. My takeaway from college physics class was that (assuming there's no saturation in the material) the...
  10. Shahsquatch

    Magnet Fundamentals and Iron Powder

    I am creating a product that incorporates magnetic sensing of magnetic nanoparticles. However due to their cost, I have decided to search for other avenues of testing. My question is about whether Iron Powder will retain a magnetic field once magnetized. I basically will place some iron powder...
  11. E

    Force on a ferrous object inside a non-uniform magnetic field

    Hello everyone! I want to know how to compute the force applied on ferrous inside a non-uniform magnetic field, to make it easier, let's assume that the field direction is constant, and the magnitude decreases linearly. Now, I know that ferromagnetic material inside a magnetic field will...
  12. B

    I Lab experiment: hysteresis disappears, reappears and then disappears again. How?

    Hi people, In my college laboratory we were assigned an experiment to measure the hysteresis curves of a certain ferromagnetic material at different temperatures. Sounds simple, right? Well, the block of Monel 400 we chose did something weird. We cooled it down to about -200°C and set about to...
  13. S

    Heisenburg Ferromagnetic Model

    Homework Statement There are several parts to this question, however I could complete these parts. It is just an equation used in the prior part to the question that is need to solve this: If we define \begin{equation} \sigma_{n}^{-}=\sigma_{n}^{x}+i\sigma_{n}^{y} \end{equation} and with the...
  14. C

    Magnetic field of a ferromagnetic cylinder

    Homework Statement We have a very long ferromagnetic cylinder with square cross section, with side length a. Cylinder is homogeneosly magnetized over his volume so that the magnetization vector is parallel to the axis of cylinder. Cylinder is in vacuum. Find the current appeared in the cylinder...
  15. N

    Will ferromagnetic dust retain magnetism in molten aluminum?

    Curie temperature for magnetite is 858 C, for iron 1043 C. Duralumin melting point is about 630 C. Does this mean that if I take a small silicone mold, place a magnet underneath it, add ferromagnetic powder to the mold and then pour molten aluminum in, I will get the aluminum detail with...
  16. K

    Ferromagnetic Heisenberg Model

    Now after applying and removal magnetic field H=0 there will be residual magnetic domain in XYZ directions Is the Heisenberg Model at very low temperature express about the energy of the system with higher accuracy than Ising Model in the previous case ? and at high temperature is the Ising...
  17. G

    Permeability in ferromagnetic material (AC)

    Homework Statement The following coil-wound core (core length = L , Gap length = lg, cross- sectional area = A , core permeability = only hysteresis graph is given, N = N turns) is driven by a Voltage source, is known that the current in the coil is 60hz AC. Determine...
  18. T

    Looking for what I thought would be a simple Permeability Q

    Hi, I've been thinking about how to calculate a permeability curve, I thought this would be an easy to find online but unfortunately I haven't had any luck. From what I can graphically see below: It appears to me that mu for a ferromagnetic material is proportional to the derivative of B vs H...
  19. R

    What are the properties of ferromagnetic powder?

    Hello! I am trying to understand a few properties of the ferromagnetic powder.I could not get the answers to these questions on the web, since any kind of phrasing i used, popped up search results that related to iron powder or ferromagnetic powder, which are manipulated and shape-shift using...
  20. S

    Magnetic anode for copper cathode battery

    Hello everyone from the Physics Forums, I'm doing a school project and I'm looking for a potential anode alloy that is ferromagnetic which I could use with a copper cathode. I'm making a battery and I have to use copper as my cathode mainly because I have made the cathode cells structured...
  21. M

    What happens when external magnetic field is applied to ferromagnetic materials?

    Hello everyone. I'm not entirely sure if this is the right section to post this question in but if it isn't, then I apologize. I'm studying for a test in E&M and I've come across a topic that had me thinking and I'm not quite sure if the explanation I'm thinking of is entirely true. Please...
  22. 2

    Magnetic attraction to ferromagnetic material

    Why do magnets attract ferromagnetic materials only? Why not other materials as well?
  23. T

    Why are Fe, Ni, Co ferromagnetic among metals?

    What makes Fe, Co and Ni ferromagnetic compared to all other metals (with exception of Gd, Dy and some exotic alloys according to Wikipedia)? If other ferromagnetic metals just have lower Curie temperatures then why is it so? Sub-question: In pure metals is there any correlation in magnetic...
  24. J

    Can Ferromagnetic Objects Be Decomposed Using Magnetism?

    I have came up with a theory, it could be completely wrong or not but i had the idea of ferromagnetic decomposition and what i mean by this is breaking a ferromagnetic object apart (such as iron) using magnetism. Is this possible or not?
  25. S

    Ground State Degeneracy in ferromagnetic Heisenberg model

    I am reading the book "Lecture notes on Electron Correlation and Magnetism" by Patrik Fazekas. It says, "The ground state (of Heisenberg FM model) is not unique. We have just found that the system has the maximum value of the total spin Stot = LS. Sztot = LS state which is maximally...
  26. H

    What is ferromagnetic memories ?

    What is ferromagetic memories ? I need matter on this help me please, searching so many webs can't get proper matter :(
  27. S

    EMF Meters and Ferromagnetic Interference

    Hi, My interest in physics is relatively new and recently I've been trying to figure out the answer to what is probably a simple question. Here it is; if one is using an AC EMF meter to read the time varying current from a man-made electromagnetic field, will brandishing ferromagnetic...
  28. A

    Ferromagnetic resonance oscillating field strength

    Hello. What oscillating field strength, in tesla, is required to cause the magnetization vector of a ferromagnetic material to precess with a fairly large angle at its resonance frequency? I can't find this number anywhere!
  29. V

    What are the properties and applications of ferromagnetic thin films?

    Hi, I am doing my PG. To select a topic for my mini project, I select the topic "Ferromagnetic thin films" Probably I will be covering it's properties, fabrication and applications at some basic level. So what is the problem is I have no one to guide me here as I am far away from the...
  30. V

    What is the minimum thickness required for ferromagnetism in thin films?

    Hi, I am doing my PG. To select a topic for my mini project, I select the topic "Ferromagnetic thin films" Probably I will be covering it's properties, fabrication and applications at some basic level. So what is the problem is I have no one to guide me here as I am far away from the college...
  31. P

    Exploring Resistance in a Ferromagnetic Circuit

    Homework Statement Electrons in a ferromagnet whose spins are oriented in the direction of, or opposite to, the internal magnetisation carry independent currents I+ and I−. This leads to the material behaving as though it has different conductivity σ+ and σ− for each of the two current...
  32. T

    Why does saturation of a ferromagnetic result in non-sinusoidal current?

    Hello... I have a question: Physically why when a ferromagnetic is saturated the current is non-sinusoidal ( I'm taking the example of the magnetising current of a transformer). I know graphically and mathemeticalty why( from the hysteresis loop) but In reality what happens(I'm talking about...
  33. fluidistic

    Induction oven, ferromagnetic

    I do not understand why ferromagnetic materials are more easily heated by an induction oven than a non/low ferromagnetic material such as copper or aluminum. Are Eddy currents more easily induced into a ferromagnetic material than a conductor lacking a high ferromagnetic property? Why is it so?
  34. matt_crouch

    Calculate the spin wave dispersion relation for a ferromagnetic heisenberg model

    Homework Statement Calculate the spin wave dispersion relation Ek for the ferromagnetic Heisenberg model with jtot = 1/2 Assume a 1d square lattice and interactions of strength J between nearest neighbours and zero elsewhere Homework Equations H|k> = [E0 +2jtot\sum J(r)(1-Exp(ik.r) ]...
  35. J

    How to find inductance of a coil with two concentric ferromagnetic cores?

    Homework Statement This isn't exactly a homework question so there aren't any data/numbers to work with. I just want to know what to do if there are two ferromagnetic cores inside a coil of wire, arranged as concentric cylinders. Or how to account for the air gap between the core and the coil...
  36. C

    Magnetic Field near a Ferromagnetic Object

    Considering a bar of ferromagnetic (FM) material (eg, Nickel) placed in a uniform magnetic field (eg, B = 1kG along x). I know the H field produced by a given magnetization M of the ferromagnet (ie, I have \vec{H}=M \cdot \vec{\alpha} for a calculated alpha). How do I determine the total...
  37. A

    Decrease permeability of ferromagnetic materials

    Hello. I know very few things about solid state physics, so my question is very basic.. I'm just searching for a clue.. Have some of you ever heard about, or imagine a way, of decreasing the permeability of a ferromagnetic material? Not by raising temperature, but with electric field or...
  38. F

    Magnetic scalar potential for a toroidal ferromagnetic core

    Homework Statement Given a toroidal core, with known μr, minor radius R1, major radius R2, height h (the section is not a circle, but a rectangle (R2-R1)×h), placed in a magnetic field B0 with cylindrical axisymmetries (B0r=0, B0θ=0, B0z=B0), find the magnetic field resulting by the...
  39. K

    Spin direction through ferromagnetic material

    What is the spin direction of the electrons through the ferromagnetic material? It will become parallel or antiparallel? I was confused because the scattering rate and conductivity both depend on the density of state at Fermi level. For ferromagnetic material, is it right to say that at the...
  40. Roodles01

    Dia, para & ferromagnetic materials

    From another thread I think I understand that ferromagnetic material can exist any time, but dia & para magnetic materials exist only when there is an external field. My overview is Macroscopically ferro materials have to align their domains & can remain aligned when field is removed...
  41. J

    Saturated paramagnetic and ferromagnetic

    Dear All, I have a paramagnetic material, its magnetic moment will saturate at magnetic field of 30 T (all spins align in the field direction). So shall I treat the high field phase as a ferromagnetic phase when I do electronic calculations?
  42. G

    Force exterted on a ferromagnetic object in a magnetic field

    Hello, I'm building a coilgun and I'm confused. I understand that within a solenoid, the magnetic field is homogeneous. I've also read that a ferromagnetic projectile in a coilgun is sucked to the center of the coil. If the magnetic field is the same everywhere through the coil, what is...
  43. A

    Fermi Vector in Ferromagnetic Material

    Homework Statement Consider an electron gas of density n_{0} in three dimensions that is completely ferromagnetic: all electron spins point in the same direction. Derive: a) The Fermi wave vector in terms of n_{0}. b) The parameter r as the radius in atomic unites that encloses one unit of...
  44. V

    The Impact of Ferromagnetic & Diamagnetic Materials on Magnetic Fields

    What is the effect of inserting any ferromagnetic, diamagnetic etc in magnetic field?? let me say there is a solenoid of turns per unit length n.magnetic field inside the solenoid will ~μnI. what will happen if an ferromagnetic substance like iron is inserted. How will it effect the magnetic...
  45. J

    Ferromagnetic hysteresis loop

    For a ferromagnetic material in the hysteresis loop, when increasing field from H=Hc, its magnetization (M) will saturate. But if we decrease field instead, will M decreases clockwise according to the loop? How can we make the ferromagnetic material back into the initial state (H=0, M=0)...
  46. C

    Attraction of magnets to ferromagnetic materials with distance?

    all i can find on the internet are the attractive and repulsive forces between 2 magnets... where can i find the relationship between distance and attractive force , between a magnet and i.e. a piece of iron?
  47. B

    Show that for a ferromagnetic material the field in the gap is given by?

    Homework Statement A toroidal shaped magnetic material of radius, a, and cross sectional radius R has a small transverse gap cut into it of length l. The toroid is uniformly overwound with a coil of N loops carrying a current I. Show that for a ferromagnetic material the field in the gap is...
  48. Low-Q

    Curie point for ferromagnetic materials

    Hi, I have searched the web for a graph that shows the ferromagnetic properties of a metal like iron or nickel as they warms up to the Curie temperature - when the metals becomes non-ferromagnetic. I cannot find any good images or graphs that shows this very clear. I have been told that the...
  49. A

    Ferromagnetic energy question

    Consider a brick-shaped ferromagnetic of relative magnetic permeability µ >> 1, which has dimensions 2a × 2a × a and a narrow slit of width d and depth a sawed into it as shown in Figure. You may assume that µd >> a >> d. A circular loop of diameter a and inductance L, made of a superconducting...
  50. C

    Attraction between ferromagnetic materials in a magnetic field: what is this?

    Hello! Just so you know, I am a high school student. I am asking about this because I am an IB student and doing an extended essay (it's basically research, and a bunch of experimentation to answer a research question) on something related to magnetic fields, ferromagnetic materials, or...