Overview of Ferrite Magnets

Ferrite magnets, also known as ceramic magnets or hard ferrites, were first developed in 1930 by Dr. Yogoro Kato and Dr. Takeshi Takei at the Tokyo Institute of Technology. These non-metallic permanent magnets are made using Iron Oxide (Fe2O3) combined with either Barium Carbonate (BaCO3) or Strontium Carbonate (SrCO3) as raw materials. They are manufactured through a powder metallurgy process and are typically dark grey in color, commonly shaped as arcs, blocks, discs, or rings.

While modern rare earth magnets boast superior magnetic properties, ferrite magnets remain the most widely produced permanent magnetic material globally by weight, largely because of their excellent cost-efficiency. Additionally, ferrite magnets are highly chemically stable, making them suitable for various environments. In 2020, approximately 900,000 tons of ferrite magnets were produced, serving numerous applications. Among their most notable uses are in permanent magnet (PM) motors, loudspeakers, and magnetic separators.

Ferrite Magnets-Main

Magnetic Properties of Ferrite Magnets

Ferrite magnet grades are classified under three naming systems: the United States Industry Standard, the International Electrotechnical Commission (IEC) Standard, and the Chinese Standard.

  • IEC Standard: Primarily used in Europe, this system defines grades based on the simplified values of the minimum energy product (measured in kJ/m3) and intrinsic coercivity (measured in kA/m) in SI units.
  • United States Standard: In the U.S., ferrite magnet grades are often denoted with the letter “C” followed by a number, such as the widely recognized C5 and C8 grades.
  • Chinese Standard: With China leading global ferrite magnet production, the Chinese naming convention has become the most influential. Grades begin with the letter “Y,” an abbreviation for “permanent magnet” in Chinese pinyin. The number that follows indicates the nominal energy product, while any additional letters specify the series.

The Chinese system’s widespread adoption reflects its dominance in the global ferrite magnet market and its capacity for precision in grade identification.

Magnetic Properties Chart of Ferrite Magnets
Standard Grade Remanence

Br

 Coercivity

Hcb

 Intrinsic Coercivity

Hcj

 Max. Energy Product

(BH)max
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 Magnets
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 / Tc ℃ 450
Recoil Permeability / μrec – 1.05 ~ 1.30

Physical Properties of Ferrite Magnets

Ferrite magnets offer unparalleled cost-effectiveness, along with exceptional resistance to heat, corrosion, and oxidation. Additionally, they possess insulating properties, making them suitable for applications requiring electrical isolation.

However, the long-term stability of ferrite magnets is limited by their poor mechanical properties. Due to their brittle nature, ferrite magnets cannot withstand impact or flexing, making them unsuitable for use as structural components. This characteristic necessitates careful handling and design considerations to ensure their performance and durability in various applications.

Physical Properties Chart of Ferrite Magnets
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

Magnetization Directions of Ferrite Magnets

Before being utilized in their final applications, most permanent magnets, including ferrite magnets, must undergo a magnetization process. This process involves applying an external magnetic field in a specific direction until the magnet reaches saturation. Compared to Neodymium or Samarium Cobalt magnets, ferrite magnets are relatively easier to magnetize and demagnetize.

Ferrite magnets are categorized into isotropic and anisotropic types based on their magnetization orientation. Isotropic ferrite magnets have no preferred magnetization direction, allowing them to be magnetized in any desired direction. In contrast, anisotropic ferrite magnets possess a predefined magnetization direction and can only be magnetized along this orientation.

For anisotropic ferrite magnets, various pole configurations can be achieved, provided they align with the predetermined orientation. This versatility makes ferrite magnets suitable for a wide range of applications requiring specific magnetic properties.