You've probably done it. Held a fridge magnet up to a stainless steel sink and wondered why nothing happened. Or watched a kid try to pick up a copper penny with a horseshoe magnet, confused when it just sat there.
Here's the thing — most people think magnets stick to metal*. Period. But that's not how it works. Not even close.
What Is Magnetic Attraction Anyway
Magnets don't care about "metal" as a category. They care about electron configuration. Specifically, unpaired electrons in the d-orbital or f-orbital that can align their spins in the same direction.
When that happens at the atomic level across millions of atoms, you get a magnetic domain. Still, when those domains align, you get a macroscopic magnetic field. Now, that's it. That's the whole secret.
Ferromagnetism — the heavy lifter
This is what people mean when they say "magnetic.Even so, the domains scramble. Their atoms have unpaired electrons that want* to align. " Iron, nickel, cobalt, and gadolinium at room temperature. They do it spontaneously below their Curie temperature. Still, above that temperature? Thermal vibration wins. Magnetism vanishes.
Iron's Curie point is 770°C. Nickel's is 358°C. Cobalt holds on until 1,115°C. Heat a nail red-hot with a torch, let it cool, and it'll still stick to a magnet. Because of that, heat it past* that point and let it cool in zero field? Dead. No magnetism left.
Ferrimagnetism — the ceramic cousin
Ferrites. In practice, magnetite (Fe₃O₄). The black sand you find at the beach. Because of that, these are metal oxides, not pure metals, but they behave similarly — strong attraction, permanent magnetization possible. So your fridge magnet? Think about it: almost certainly a ceramic ferrite. Cheap, brittle, works fine.
Paramagnetism — the "technically yes but practically no" category
Aluminum. Platinum. Here's the thing — manganese. Oxygen (yes, liquid oxygen is paramagnetic). These have unpaired electrons too, but they don't align spontaneously. They need an external* field to nudge them. Practically speaking, the effect is weak — thousands of times weaker than ferromagnetism. Even so, you won't feel it with a handheld magnet. But in an MRI's 3-tesla field? Different story.
Diamagnetism — everything else, basically
Copper. Silver. Gold. On top of that, lead. Water. Your finger. Plus, All materials have some diamagnetic response — a weak repulsion from magnetic fields. It's just so tiny you never notice. Except with superconductors (perfect diamagnetism) or absurdly strong fields. There's a famous video of a live frog levitating in a 16-tesla field. The frog is fine. Mostly confused.
Why It Matters / Why People Care
You're not reading this for trivia. Day to day, you're reading it because you tried to magnetize something and it failed. Or you're designing something and need to know what'll stick.
The stainless steel trap
This is the big one. Which means people buy "stainless" appliances expecting magnets to work. Half the time they don't.
Austenitic stainless (300 series — 304, 316) is non-magnetic. Which means nickel content stabilizes the face-centered cubic structure. Probably 304. No ferromagnetism. Practically speaking, your fancy fridge? Magnets slide right off.
But ferritic stainless (400 series — 430, 409) is magnetic. Less nickel, body-centered cubic structure. Cheaper. Used in car exhausts, some budget appliances. Magnets stick fine.
Martensitic stainless (410, 420, 440) — also magnetic. Hardenable. Knives, surgical tools, turbine blades.
Duplex stainless? Mixed. Which means partially magnetic. Depends on the exact phase balance.
If you need magnets to stick to stainless, check the grade. Don't assume.
Scrap sorting — the real-world test
Walk into any scrap yard. The guy with the magnet on a crane? He's separating ferrous from non-ferrous in seconds. Even so, iron and steel go one way. Copper, aluminum, brass, stainless (austenitic) go the other. Still, price difference is massive. That magnet just paid for itself a thousand times over.
Engineering decisions
Designing a magnetic latch? Specifying 304 for a magnetic holder? A sensor mount? You need to know exactly what's ferromagnetic and what isn't. Specifying 303 stainless for a part that needs to be magnetically invisible? Smart. Worth adding: a motor rotor? Expensive mistake.
How It Works — The Metals That Actually Stick
Let's get specific. Here are the metals and alloys that show strong ferromagnetic attraction at room temperature.
Pure elements (only three at room temp)
Iron (Fe) — The king. Body-centered cubic. 2.2 tesla saturation. Cheap, abundant, rusts like crazy unless alloyed or coated. Pure iron is soft — you can bend a rod with your hands. But it's the base for everything that matters.
Nickel (Ni) — Face-centered cubic. 0.6 tesla saturation. More corrosion resistant than iron. Used in alloys (Alnico, Mu-metal, stainless), plating, batteries. Not strong enough alone for most structural magnets.
Want to learn more? We recommend j chem inf model impact factor and liquid crystalline polymer electron probe microanalysis for further reading.
Cobalt (Co) — Hexagonal close-packed at room temp. 1.8 tesla saturation. Holds magnetism at higher temperatures than iron. Expensive. Critical for high-temp alloys, superalloys, some permanent magnets (SmCo).
Gadolinium (Gd) — Ferromagnetic below* 20°C (68°F). Above that, paramagnetic. So at room temperature it's right on the edge. Cool it slightly and it sticks. Warm it slightly and it lets go. Neat party trick. Not practical for much.
The alloys that matter more than pure metals
Carbon steel — Iron + carbon (up to ~2%). The workhorse. Magnetic properties vary with carbon content and heat treatment. Low carbon = soft magnetic (easy to magnetize, easy to demagnetize). High carbon = harder magnetic. Used in transformer laminations, motor cores, and yes — permanent magnets in the pre-rare-earth era.
Silicon steel (electrical steel) — Iron + 1–3% silicon. Higher resistivity = lower eddy current losses. Grain-oriented (GOES) for transformers. Non-grain-oriented (NGOES) for motors. Not a permanent magnet material, but magnetically soft* — it conducts flux beautifully.
Nickel-iron alloys — Permalloy (80% Ni, 20% Fe), Mu-metal (77% Ni, 16% Fe, 5% Cu, 2% Cr). Extremely high permeability. Used for magnetic shielding. Not permanent magnets — they conduct* magnetism, they don't stay* magnetized.
Alnico — Aluminum + nickel + cobalt + iron. The classic permanent magnet before rare earths. Cast or sintered. Temperature stable. Still used in guitar pickups, sensors, high-temp apps. Weaker than neodymium but doesn't shatter.
Ferrites (ceramic magnets) — Iron oxide + barium or strontium carbonate. Cheap. Brittle. Moderate strength. Your fridge magnet. Speaker magnets. Millions of tons made yearly.
Neodymium-iron-boron (NdFeB) — The beast. Strong
est permanent magnet available. It allows for miniaturization of everything from hard drives to EV motors. Also, the downside? In practice, high remanence, high coercivity. Sintered powder metallurgy. It oxidizes rapidly and can shatter under impact due to its crystalline structure.
Samarium-cobalt (SmCo) — The high-temp alternative to Neodymium. Strong, but not as strong as NdFeB. On the flip side, it is far more resistant to corrosion and maintains its magnetic strength at temperatures where Neodymium would simply give up. Critical for aerospace and military applications.
The "Almost" Metals: The Great Confusions
To understand what sticks, you have to understand why some things almost* stick, leading to the "Expensive Mistake" mentioned earlier.
The Stainless Steel Trap
Not all stainless steel is created equal. The magnetism depends entirely on the crystal structure:
- Austenitic (300 series, e.g., 304, 316): These have a face-centered cubic structure. They are generally non-magnetic. If your magnet doesn't stick to your "stainless" sink, it's likely austenitic.
- Ferritic (400 series): These have a body-centered cubic structure (like iron). They are strongly magnetic.
- Martensitic: Also magnetic. These are the harder steels used in knives.
- The Twist: Cold-working (bending or machining) austenitic steel can actually transform some of the structure into martensite, making a "non-magnetic" piece of steel suddenly attract a magnet in specific spots.
Paramagnets and Diamagnets
Then there are the metals that technically react to magnets, but not in a way you can feel.
- Paramagnetic (Aluminum, Platinum, Magnesium): They are weakly attracted to magnetic fields, but the effect is so minuscule it requires laboratory equipment to detect.
- Diamagnetic (Copper, Gold, Silver, Bismuth): These actually repel* magnetic fields. Again, the force is nearly invisible to the naked eye, but it's why a powerful neodymium magnet can actually levitate a small piece of pyrolytic graphite.
Conclusion: Choosing Your Material
When selecting a metal for a magnetic application, the choice boils down to a trade-off between permeability (how well it conducts flux), coercivity (how hard it is to demagnetize), and cost.
If you need a temporary bridge for magnetic flux, go with silicon steel. If you need a cheap, rugged magnet for a consumer product, ferrites win every time. If you need to shield a sensitive electronic component from interference, Mu-metal is your only real option. But if you are fighting for every millimeter of space and need maximum lifting power, Neodymium is the undisputed king.
Just remember: before you trust your expensive workpiece to a magnetic holder, check the grade of your steel. Because in the world of metallurgy, the difference between "sticks" and "slides" is often just a few percentage points of chromium and nickel.
