Q: What causes iron, nickel, and cobalt to be attracted to magnets, but not other metals?

Physicist: The magnetic properties of a material are governed entirely by the configuration of the electrons in that material.  In metals there are two types of electrons: bound electrons and free electrons.  The free electrons are free to move between atoms, and are the cause of conductivity in metals.  The bound electrons are stuck to the individual atoms.

Each electron, in addition to having charge, also has a “magnetic moment” which is a fancy way of saying that it’s a tiny bar magnet.  Generally the bound electrons will be paired off in opposite spin pairs.  This is like putting a North-South magnet next to a South-North magnet.  They almost completely cancel each other out.  However, sometimes (in iron, nickel, and cobalt for example) you’ll have one or more un-paired electrons.  The magnetic fields of these electrons aren’t canceled out by another, oppositely-oriented, electron.  As such they lend an overall magnetic field to the atom they inhabit.

So, some metals are attracted to magnets because they are full of tinier magnets.  Those tinier magnets twist about so that they align with the field of the larger magnet.  However, that just pushes the question back to “Why do magnets attract each other?”.

Those free electrons aren’t completely useless.  If they’re exposed to a changing magnetic field (wave your magnet around) they’ll start moving around in “eddy currents”.  Those eddy currents always try to resist the changing field (“Lenz’s law” or “the universe is a stubborn jerk law”).  So all conductive metals interact with magnetic fields (otherwise generators wouldn’t work), but not in the “attracted to” kind of way.


Answer gravy: “Why do magnets attract each other?”  Magnetic fields, like high school students, don’t really want to exist.  A magnetic field of strength B that fills up a volume V has an associated energy E=\frac{B^2}{8\pi}V.  So creating magnetic fields takes energy, and getting rid of them frees up energy.

It turns out that processes that release energy are usually forces.  For example; when you drop an object energy is released, and it so happens that gravity is a force.  Similarly, magnets will try to line up in such a way that they will cancel out each other’s fields.  Less fields = less energy.  So, the process of lining up to cancel out their fields decreases the energy tied up in those fields, and as such there’s a force that tries to line up the magnets.


Also: The physics behind the magnetic properties is really nasty.  Nasty enough that the math can’t be done, and computer simulations can’t be trusted (generally).  Here’s a map of the (experimentally found) magnetic properties on the periodic table:

Some patterns, but lots of exceptions as well. The magnetic properties of the heavier elements are difficult to study, since they generally have half-lives of substantially less than a second.

This entry was posted in -- By the Physicist, Physics. Bookmark the permalink.

29 Responses to Q: What causes iron, nickel, and cobalt to be attracted to magnets, but not other metals?

  1. why some metals are not attracted to magnets?
    please answer via email: b7a_b7a23@yahoo.com

  2. Venkataraman says:

    How do any material gets color?

  3. joe coffey says:

    what type of magnet would you use to seperate cobalt from cast sands

  4. Vishal kanwar says:

    Why does heavier iron piece attracts lighter
    Magnet piece

  5. sajjad says:

    آیا آهنربایی داریم که فلز رو دفع کند؟

  6. Aliyah says:

    okay so this is yo much reading and I have a paper do tomorrow and I need to learn about the element nickel. Thank you for your time and I will be back and I’m a newspaper writer

  7. kamalraj says:

    To which nuclei do the bonding electrons of a covalent bond revolve round ?

  8. harshil borda says:

    if we put magnet in box which is made up of lead then?

  9. sunny says:

    all conductive metals like cu and al are having free electron then why not they are conductive in nature?

  10. ahmad says:

    Summy cobalt ion and nickel have parallel spins and the magnetic feild of the electrons doesn’t cancel out.

  11. hannah deleon says:

    why those iron,cobalt and nickel are attracted to the magnets???

  12. William Hoffman says:

    You show Al as paramagnetic, but Cu as diamagnetic. Both show Lenz effect with a strong magnet. How can that be? TIA

  13. moreshwar h. warambhe says:

    I have read various articles regarding why does magnet attract,but still I am not satisfied,because I yet to understand how does field created and how it attracts and repell.

  14. ravi gupta says:

    Next time will say . .

  15. Salvi says:

    Why are some materials attracted to magnets and others are not?

  16. Jatin rohilla says:

    Very good answers

  17. PREETHI BASKARAN says:

    How will the magnet work, when it is used for the collection of metallic objects from the dustbin and then at particular time, the metallic objects should be released into the separate section of the dustbin (without magnetization), is it possible?

  18. pouangam kameni jerome says:

    Why is that iron losses it magnetic property after some time

  19. tapiwa says:

    why is it that some metals are used to make magnets while others cannot be used. Reply via email

  20. Ramadan Adem says:

    Why will not a magnet attract a piece of copper??

  21. Navanjana Abisheka Gamalath says:

    I want to know whether tungsten has magnetic properties and why some pieces of sand, granite and other stone particles are attracted towards magnets? And also I want to know why the bound electrons of an atom paired off in opposite pairs and why it does not take place in iron, nickel and cobalt like elements completely? I want an exact answer for it. You have given that iron, nickel and cobalt possess one or more unpaired electrons and because of that the magnetic fields of these electrons aren’t cancelled out by another oppositely oriented electrons. It is absolutely correct. But the metals such as Mn, Cu, Al, Cr also possess unpaired electrons know. Mn has 5 unpaired electrons, Cr has 6, 1 from ‘s’ orbital and the other 5 from ‘d’ orbital, Al and Cu each possess 1 unpaired electron. But iron has 4 unpaired electrons, nickel has 2 and cobalt has 3 unpaired electrons each. So why do the metals like Cr,Mn, Al and Cu are not attracted by magnets? They also possess unpaired electrons know? Please e-mail me and explain this to me in details. Thank you for providing me with
    some valuable information about the magnetism.

  22. John Smith says:

    The difference for non magnetic materials versus Ni, Co and Fe is that the electrons travel along orbitals that, though most are paired within the orbitals, in some cases an up spin can be countered by a down spin from an electron that is physically in another orbital yet close enough to make an impact mitigating the induction of the magnetic field. In the case of the big 3, that offsetting spin from another orbital is missing, thereby allowing just enough unpaired electrons to spin freely, inducing the magnetic moment.

  23. boo says:

    i want to know why is cobalt attracted to a bar magnet

  24. boo says:

    i want to know why is cobalt attracted to a bar magnet

  25. Boo says:

    can u harry up and tell me why cobalt attracted to a bar magnet

  26. Anonymous says:

    Unsubscribe me from these services

  27. Big Dog Big Homy says:

    I like it.

  28. Anonymous says:

    what does this all mean?

Leave a Reply

Your email address will not be published.