Hi! Which element is
attracted the most to a magnet?
Is it a clear winner,
or is there any competition for it?
I will test the best candidates at room temperature
and an outsider just below that
temperature in four different experiments.
Going into this, I thought there
would be a clear winner
but I was surprised by the results.
Maybe you will be too?
Strong magnets will bite you at any given chance.
Do be careful with them.
And wear safety glasses when using them.
You'll see why later...
Nickel and cobalt can cause skin problems
so don't wear them as jewellery.
Overall there are three ways
a material can react to a magnet.
Diamagnetic materials are
weakly repelled by a magnet.
Materials that are paramagnetic
are weakly attracted to a magnet
but can't be magnets in themselves.
And then there are the ferromagnetic materials
which are strongly attracted to a magnet
and can be magnets in themselves.
The ferromagnetic materials are
what we call magnetic in everyday speech
so obviously we have to look for the strongest
attractions in the ferromagnetic elements.
There are only three of these:
Iron, nickel and cobalt.
At room temperature...
If we go just below room temperature
gadolinium also turns ferromagnetic.
Since "just below room temperature" is
a normal temperature in Denmark
I consider gadolinium a ferromagnetic element
and will include it in the tests.
First test is the most obvious.
Place samples of similar size
on top of a powerful magnet
and see how much force it takes to remove
the samples from the magnet again.
I will use this spring balance
and zero it before each test
so the weight of the container and
sample doesn't count as pull force.
I'll start with cobalt.
This element is used in strong samarium-cobalt magnets and cheaper alnico magnets.
Seems like we can expect it to do well.
I will measure at two spots:
The center of the magnet and at the edge,
where the magnetic field is stronger.
At the center, the pull force needed to
remove the cobalt rod is around 1.4 kg.
At the edge, the magnetic field curls
hard down towards the other pole
making the rod switch position.
With more of the rod close to the magnet
- and in a stronger magnetic field -
the pull force will be much higher.
Looks like 5.2 kg for cobalt.
Not a bad start!
Next up is nickel.
It is used in the relatively
weak alnico magnets
and as coating on neodymium magnets
so I'm not expecting nickel to
perform as well as cobalt.
The pull force on the center is a mere 600 g.
On the edge, it is 1.4 kg.
Similar to cobalt on the weaker center...
Let's switch to my favorite contender:
Iron.
This element is the main part
of the neodymium magnets
the strongest permanent magnets we know of
and also used in ferrite and alnico magnets.
It should perform well.
Ohohoh yes, almost 2 kg on the center.
It must be high on the edge then...
It sure is!
6.3 kg is very impressive
for a small 12 g sample.
How about the outsider gadolinium?
It is not a main part of
any commercial magnets.
It can be used to make neodymium magnets
more resistant to demagnetization.
Especially at higher temperatures.
But dysprosium seems to be prefered for this.
Here in my living room, gadolinium is
only paramagnetic but let me test it anyway.
At the center, it doesn't align vertically
with the magnetic field like the others.
A sign of it not being
magnetized like a ferromagnet.
But for comparable results, I will
measure it standing up like the others.
400 g pull force -
not bad for a paramagnetic material.
Almost as good as the ferromagnetic nickel.
It does surprisingly well
at the edge too: 1.2 kg.
Now, I'm really curious to know
how it performs in its ferromagnetic state.
Depending on different sources
The transition should happen between 16 to 20°C.
That's very convenient
because even in a warm winter
it is cold enough in my sunroom
to turn gadolinium ferromagnetic.
Let's see if it really works...
Well, it clearly is a different reaction.
Now, it aligns vertically like
the other ferromagnets.
Isn't that amazing?!?
The only difference is 10°C.
Let's see how it performs.
On the center, it has increased to 600 g.
The same as nickel.
But on the edge...
It is now almost 2 kg.
Better than nickel.
The conclusion of the pull force test is,
that iron is the winner.
Not a surprise...
Afterall it has Fe printed on it.
The first two letters in ferromagnetism.
Ferrum is latin for iron,
and ferromagnetism is named after iron.
It is more surprising that gadolinium in its paramagnetic
state is so close to the ferromagnetic nickel.
Maybe my spring balance isn't
precise enough at the low forces?
Or is the gadolinium magnetized at room temperature?
More testing is needed...
I want to see how well the samples conduct
the magnetic field from this tiny magnet.
As a control test, I will try with 20 mm air first.
Air does not conduct the magnetic field well.
Only 3 milliteslas.
Time for a montage of the results of the
ferromagnetic elements before we test gadolinium.
All right. They maxed out between 23 to 31 mT.
Will gadolinium be any match for
these values at room temperature?
Nnnnnno. Not at all...
It isn't much better than air.
It is not showing any ferromagnetic behavior.
The ferromagnetic samples had a
stronger magnetic field at the edge.
A sign of them having poles like any other magnet.
But I don't see it on
gadolinium at this temperature.
Will we see a change at 11°C?
Yes! Now it acts like a ferromagnet.
It is as strongly magnetized as nickel
and also show higher values
at the edge like the others.
OK. So gadolinium was clearly not
magnetized in the first pull force test.
Maybe we should try with a
much more sensitive scale.
I used this milligram scale to
measure the weight of the rods.
It can be used for a
different pull force test as well.
By putting a magnet at a fixed
distance above the rod
we can see on the scale how much
the rod is lifted by the magnet.
For nickel, it is 4.8 g.
Let me show you the others.
Look out for an odd result...
Again, we see nickel winning clearly
over gadolinium at 23°C.
But.... cobalt beat iron?!?
Now, I am confused.
Is cobalt more attracted at a distance than iron?
We need to include one of my favorite tests.
The long distance test I call the water bath run.
Working with ferromagnetic
elements in this test for the first time
I wanted to get a feel for how long
I could make the water bath.
I didn't film it, but I wasn't exactly successful...
The glass slipped out of my gloved hand...
Do remember to wear safety goggles
when working with powerful magnets.
Here's the final setup.
Will cobalt beat iron again?
Cobalt wins again!
Followed strongly by nickel.
Leaving iron only to beat gadolinium...
The results from the distance tests baffle me.
I cannot explain why iron is the
strongest at the surface of the magnet
but at distance, cobalt seems to
have the highest magnetic susceptibility.
Any help and input from you
in the comments is more than welcome.
The final conclusion on my
experiments is a bit messy.
At room temperature, iron is attracted
the most to a magnet - at the surface of the magnet.
At a distance, cobalt seems to be
attracted the most to a magnet.
If we look at all temperatures
Holmium is actually the strongest
known elemental ferromagnet.
However, it has to be
cooled down below 20 kelvin.
My house is not prepared for handling
the liquid helium needed to cool it.
Yet...
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Bye for now!
