Ferrite Magnet - SDM Magnetics Co., Ltd.

A ferrite magnet, commonly known as a ceramic or hard ferrite, was first developed in 1930 by Dr. Yogoro Kato and Dr. Takeshi Takei at Tokyo Institute of Technology. This non-metallic permanent material, crafted using Iron Oxide (Fe₂O₃), Barium Carbonate (BaCO₃), or Strontium Carbonate (SrCO₃) through powder metallurgy, exhibits a distinctive dark grey color. Shaped as arcs, blocks, discs, or rings, a ferrite magnet adapts to diverse industrial needs, delivering robust, versatile forms for dependable performance across a wide range of applications.

While rare earth magnets outshine in magnetic strength, a ferrite magnet leads global permanent magnet production by weight, driven by superior cost-efficiency and chemical stability in diverse environments. In 2020, about 900,000 tons of Ferrite magnets powered key applications, with permanent magnet motors, loudspeakers, and separators serving as three primary examples, reflecting the ferrite magnet’s affordability and dependability in technological and industrial uses.

Ferrite Arc Magnets

Ferrite Block Magnets

Ferrite Disc Magnets

Ferrite Ring Magnets

Manufacturing Process of Ferrite Magnet

The production of a ferrite magnet starts with weighing, mixing, pelletizing, and calcining (pre-sintering) raw materials like Strontium or Barium Carbonate and Iron Oxide. These calcined products undergo multistage milling, reducing them to fine powder with particles under 1 micron. The powder is then packed into molds and pressed. Notably, the pressing of a ferrite magnet splits into dry and wet processes, each tailored to specific production needs for optimal outcomes.

In the wet process, fine powders blend with a solvent, forming a slurry that aligns to enhance magnetic properties. After pressing, the green body is sintered at high temperatures. Post-sintering, a ferrite magnet is machined into precise shapes and magnetized, ensuring it meets exact specifications for diverse industrial applications with reliable performance.

Magnetic Properties of Ferrite Magnet

A ferrite magnet’s grade follows three naming conventions: United States Industry Standard, International Electrotechnical Commission Standard, and Chinese Standard. The IInternational Electrotechnical Commission Standard, mainly adopted in Europe, uses simplified values of minimum energy product in kJ/m³ and intrinsic coercivity in kA/m. Conversely, the US Standard identifies a ferrite magnet with a “C” followed by a number, such as the widely recognized C5 or C8 grades, indicating specific magnetic characteristics.

China, as the primary producer, shapes ferrite magnet grading with its Chinese nomenclature system. Grades begin with “Y,” standing for permanent magnet in Chinese phonetics, trailed by a number denoting the nominal value of energy product. A subsequent letter acts as a serial identifier, distinguishing variations. A ferrite magnet under this system reflects precise categorization tailored to diverse industrial requirements.

Magnetic Properties Chart for Ferrite Magnet

Standard	Grade	Remanence Br		Coercivity Hcb		Intrinsic Coercivity Hcj		Max. Energy Product (BH)max
Standard	Grade	mT	kG	kA/m	kOe	kA/m	kOe	kJ/m³	MGOe
Chinese Standard	Y8T	200-235	2.0-2.35	125-160	1.57-2.01	210-280	2.64-3.52	6.5-9.5	0.8-1.2
	Y10T	200-235	2.0-2.35	128-160	1.61-2.01	210-280	2.64-3.52	6.4-9.6	0.8-1.2
	Y20	320-380	3.2-3.8	135-190	1.70-2.39	140-195	1.76-2.45	18.0-22.0	2.3-2.8
	Y22H	310-360	3.1-3.6	220-250	2.76-3.14	280-320	3.52-4.02	20.0-24.0	2.5-3.0
	Y23	320-370	3.2-3.7	170-190	2.14-2.39	190-230	2.39-2.89	20.0-25.5	2.5-3.2
	Y25	360-400	3.6-4.0	135-170	1.70-2.14	140-200	1.76-2.51	22.5-28.0	2.8-3.5
	Y26H	360-390	3.6-3.9	220-250	2.76-3.14	225-255	2.83-3.20	23.0-28.0	2.9-3.5
	Y26H-1	360-390	3.6-3.9	200-250	2.51-3.14	225-255	2.83-3.20	23.0-28.0	2.9-3.5
	Y26H-2	360-380	3.6-3.8	263-288	3.30-3.62	318-350	4.00-4.40	24.0-28.0	3.0-3.5
	Y27H	370-400	3.7-4.0	205-250	2.58-3.14	210-255	2.64-3.20	25.0-29.0	3.1-3.6
	Y28	370-400	3.7-4.0	175-210	2.20-2.64	180-220	2.26-2.76	26.0-30.0	3.3-3.8
	Y28H-1	380-400	3.8-4.0	240-260	3.02-3.27	250-280	3.14-3.52	27.0-30.0	3.4-3.8
	Y28H-2	360-380	3.3-3.8	271-295	3.41-3.71	382-405	4.80-5.09	26.0-30.0	3.3-3.8
	Y30	370-400	3.7-4.0	175-210	2.20-2.64	180-220	2.26-2.76	26.0-30.0	3.3-3.8
	Y30BH	380-390	3.8-3.9	223-235	2.80-2.95	231-245	2.90-3.08	27.0-30.0	3.4-3.8
	Y30H-1	380-400	3.8-4.0	230-275	2.89-3.46	235-290	2.95-3.64	27.0-32.0	3.4-4.0
	Y30H-2	395-415	3.95-4.15	275-300	3.46-3.77	310-335	3.90-4.21	27.0-32.5	3.4-4.1
	Y32	400-420	4.0-4.2	160-190	2.01-2.39	165-195	2.07-2.45	30.0-33.5	3.8-4.2
	Y32H-1	400-420	4.0-4.2	190-230	2.39-2.89	230-250	2.89-3.14	31.5-35.0	4.0-4.4
	Y32H-2	400-440	4.0-4.4	224-240	2.81-3.02	230-250	2.89-3.14	31.0-34.0	3.9-4.3
	Y33	410-430	4.1-4.3	220-250	2.76-3.14	225-255	2.83-3.20	31.5-35.0	4.0-4.4
	Y33H	410-430	4.1-4.3	250-270	3.14-3.39	250-275	3.14-3.46	31.5-35.0	4.0-4.4
	Y34	420-440	4.2-4.4	200-230	2.51-2.89	205-235	2.58-2.95	32.5-36.0	4.1-4.5
	Y35	430-450	4.3-4.5	215-239	2.70-3.00	217-241	2.73-3.03	33.1-38.2	4.2-4.8
	Y36	430-450	4.3-4.5	247-271	3.10-3.41	250-274	3.14-3.44	35.1-38.3	4.4-4.8
	Y38	440-460	4.4-4.6	285-305	3.58-3.83	294-310	3.69-3.90	36.6-40.6	4.6-5.1
	Y40	440-460	4.4-4.6	330-354	4.15-4.45	340-360	4.27-4.52	37.5-41.8	4.7-5.3
American Standard	C1	230	2.3	148	1.86	258	3.5	8.36	1.05
	C5	380	3.8	191	2.4	199	2.5	27	3.4
	C7	340	3.4	258	3.23	318	4	21.9	2.75
	C8 / C8A	385	3.85	235	2.95	242	3.05	27.8	3.5
	C8B	420	4.2	232	2.913	236	2.96	32.8	4.12
	C9	380	3.8	280	3.516	320	4.01	26.4	3.32
	C10	400	4	280	3.52	284	3.57	30.4	3.82
	C11	430	4.3	200	2.512	204	2.56	34.4	4.32
	C12	400	4	290	3.65	318	4	32	4
European Standard	HF8/22	200/220	2.00/2.20	125/140	1.57/1.76	220/230	2.76/2.89	6.5/6.8	0.8/1.1
	HF20/19	320/333	3.20/3.33	170/190	2.14/2.39	190/200	2.39/2.51	20.0/21.0	2.5/2.7
	HF20/28	310/325	3.10/3.25	220/230	2.76/2.89	280/290	3.52/3.64	20.0/21.0	2.5/2.7
	HF22/30	350/365	3.50/3.65	255/265	3.20/3.33	290/300	3.64/3.77	22.0/23.5	2.8/3.0
	HF24/16	350/365	3.50/3.65	155/175	1.95/2.20	160/180	2.01/2.26	24.0/25.5	3.0/3.2
	HF24/23	350/365	3.50/3.65	220/230	2.76/2.89	230/240	2.89/3.01	24.0/25.5	3.0/3.2
	HF24/35	360/370	3.60/3.70	260/270	3.27/3.39	350/360	4.40/4.52	24.0/25.5	3.0/3.2
	HF26/16	370/380	3.70/3.80	155/175	1.95/2.20	160/180	2.01/2.26	26.0/27.0	3.2/3.4
	HF26/18	370/380	3.70/3.80	175/185	2.20/2.33	180/190	2.26/2.39	26.0/27.0	3.3/3.4
	HF26/24	370/380	3.70/3.80	230/240	2.89/3.01	240/250	3.01/3.14	26.0/27.0	3.3/3.4
	HF26/26	370/380	3.70/3.80	230/240	2.89/3.01	260/270	3.27/3.39	26.0/27.0	3.3/3.4
	HF26/30	385/395	3.85/3.95	260/270	3.27/3.39	300/310	3.77/3.89	26.0/27.0	3.3/3.4
	HF28/26	385/395	3.85/3.95	250/265	3.14/3.33	260/275	3.27/3.45	28.0/30.0	3.5/3.8
	HF28/28	385/395	3.85/3.95	260/270	3.27/3.39	280/290	3.50/3.60	28.0/30.0	3.5/3.8
	HF30/26	395/405	3.95/4.05	250/260	3.14/3.33	260/270	3.27/3.39	30.0/31.5	3.8/3.9
	HF32/17	410/420	4.10/4.20	160/170	2.01/2.14	165/175	2.07/2.20	32.0/33.0	4.0/4.1
	HF32/22	410/420	4.10/4.20	215/225	2.70/2.83	220/230	2.76/2.89	32.0/33.0	4.0/4.1
	HF32/25	410/420	4.10/4.20	240/250	3.01/3.14	250/260	3.14/3.27	32.0/33.0	4.0/4.1
The above-mentioned data of magnetic properties and physical properties are given at room temperature. The max working temperature of magnet is changeable due to length-diameter ratio, coating thickness and other environment factors. C5 = HF26/18 = Y30; C8 / C8A = Y30H-1; C1 = Y8T / Y10T; C7 = Y26H-2;C8B = Y33; C9 = Y30H-2; C10 = Y33H; C11 = Y34; C12 = Y30H-2.

Additional Magnetic Properties of Ferrite Magnet

Parameters	Unit	Reference Range
Temperature Coefficient of Br / α(Br)	%/℃	-0.20 ~ -0.30
Temperature Coefficient of Hcj/ β(Hcj)	%/℃	0.20 ~ 0.50
Curie Temperature / T_c	℃	450
Recoil Permeability / μ_rec	–	1.05 ~ 1.30

Physical Properties of Ferrite Magnet

A ferrite magnet excels with unmatched cost-efficiency, robust resistance to heat, corrosion, and oxidation, and electrical insulation properties. However, its long-term stability is limited by weak mechanical traits. Due to their brittle nature, ferrite magnets cannot endure impacts or flexing, making them unsuitable as structural components. A ferrite magnet suits environments valuing magnetic strength and durability, ensuring consistent performance.

Physical Properties Chart for Ferrite Magnet

Parameter	Unit	Value
Density / ρ	g/cm³	4.9-5.1
Vickers Hardness / HV	–	400-700
Compression Strength	N/mm²	680-720
Coefficient of Thermal Expansion / α	10^-6/°C	C⊥: 10 C∥: 15
Electrical Resistance / ρ	mΩ·cm	1 x 10¹⁰
Thermal Conductivity / k	W/(cm·℃)	0.029
Tensile Strength / σ	Pa	34 x 10⁶
Modulus of Elasticity / λ	Pa	1.8 x 10¹¹
Flexural Strength / σ	Pa	62 x 10⁶
Compression Strength	Pa	895 x 10⁶
Poisson’s Ratio / v	–	0.28

Surface Treatment of Ferrite Magnet

A ferrite magnet, crafted from Iron Oxide, resists corrosion effortlessly, remaining unaffected when submerged in water or exposed to moisture. It withstands many organic solvents, alkaline solutions, dilute acids, and certain hydroxides, showcasing exceptional durability. Due to this superior corrosion resistance, a ferrite magnet rarely requires coatings, maintaining its integrity across diverse environments without additional surface protection.

For specialized uses, such as medical instruments, a ferrite magnet may receive surface treatments to prevent dust dispersal. Nickel plating is viable, enhancing functionality. Ferrite magnets can also be painted to mask their natural dark grey hue or polished to a mirror-like sheen for magnetic therapy products like bracelets and necklaces, achieving a lustrous, metallic appearance that elevates their aesthetic appeal.

Nickel Plated Ferrite Magnets

Mirror Polished Ferrite Magnets

Magnetization Directions of Ferrite Magnet

Permanent magnets need magnetization before final use, a process applying an external magnetic field in a chosen direction to reach saturation. A ferrite magnet magnetizes and demagnetizes more readily than Neodymium or Samarium Cobalt magnets. Ferrite magnets divide into isotropic and anisotropic types based on whether they have a preferred magnetization direction, addressing diverse industrial demands with unique magnetic characteristics tailored for specific performance.

Isotropic ferrite magnets, without a preferred direction, permit magnetization in any orientation, offering versatility. Conversely, an anisotropic ferrite magnet aligns only along a preset path, ensuring focused output. Anisotropic types support various pole configurations, provided they match the predetermined direction, enabling a ferrite magnet to deliver consistent magnetic performance for precise industrial applications.