Ring antisotropic speaker Magnet

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Soft ferrites

Ferrites that are used in transformer or electromagnetic cores contain nickel, zinc, and/or manganese compounds. They have a low coercivity and are called soft ferrites. The low coercivity means the material's magnetization can easily reverse direction without dissipating much energy (hysteresis losses), while the material's high resistivity prevents eddy currents in the core, another source of energy loss. Because of their comparatively low losses at high frequencies, they are extensively used in the cores of RF transformers and inductors in applications such as switched-mode power supplies.

The most common soft ferrites are:

• Manganese-zinc ferrite (MnZn, with the formula Mn_aZn_(1-a)Fe₂O₄). MnZn have higher permeability and saturation induction than NiZn.

• Nickel-zinc ferrite (NiZn, with the formula Ni_aZn_(1-a)Fe₂O₄). NiZn ferrites exhibit higher resistivity than MnZn, and are therefore more suitable for frequencies above 1 MHz.

Hard ferrites

In contrast, permanent ferrite magnets are made of hard ferrites, which have a high coercivity and high remanence after magnetization. These are composed of iron oxide and barium or strontium carbonate. The high coercivity means the materials are very resistant to becoming demagnetized, an essential characteristic for a permanent magnet. They also conduct magnetic flux well and have a high magnetic permeability. This enables these so-called ceramic magnets to store stronger magnetic fields than iron itself. They are cheap, and are widely used in household products such as refrigerator magnets. The maximum magnetic field B is about 0.35 tesla and the magnetic field strength H is about 30 to 160 kiloampere turns per meter (400 to 2000 oersteds).^[3] The density of ferrite magnets is about 5g/cm³.

The most common hard ferrites are:

• Strontium ferrite, SrFe₁₂O₁₉ (SrO·6Fe₂O₃), a common material for permanent magnet applications.

• Barium ferrite, BaFe₁₂O₁₉ (BaO·6Fe₂O₃), a common material for permanent magnet applications. Barium ferrites are robust ceramics that are generally stable to moisture and corrosion-resistant. They are used in e.g. subwoofer magnets and as a medium for magnetic recording, e.g. on magnetic stripe cards.

• Cobalt ferrite, CoFe₂O₄ (CoO·Fe₂O₃), used in some media for magnetic recording.^[

• Sintered NdFeB Magnet
  Grade	Residual Induction  (Br)		Coercive Force (Hcb)		Intrinsic Coercive Force (Hcj)		Max Energy Product (BH)max		Max Working Temp.
  	T	kGs	kA/m	kOe	kA/m	kOe	Kj/m³	MGOe	(°C)
  N35	1.17-1.22	11.7-12.2	≥868	≥10.9	≥955	≥12	263-287	33-36	80
  N38	1.22-1.25	12.2-12.5	≥899	≥11.3	≥955	≥12	287-310	36-39	80
  N40	1.25-1.28	12.5-12.8	≥907	≥11.4	≥955	≥12	302-326	38-41	80
  N42	1.28-1.32	12.8-13.2	≥915	≥11.5	≥955	≥12	318-342	40-43	80
  N45	1.32-1.38	13.2-13.8	≥923	≥11.6	≥955	≥12	342-366	43-46	80
  N48	1.38-1.42	13.8-14.2	≥923	≥11.6	≥955	≥12	366-390	46-49	80
  N50	1.40-1.45	14.0-14.5	≥796	≥10	≥876	≥11	374-406	47-51	60
  N52	1.43-1.48	14.3-14.8	≥796	≥10	≥876	≥11	390-422	49-53	60
  N35M	1.17-1.22	11.7-12.2	≥868	≥10.9	≥1114	≥14	263-287	33-36	100
  N38M	1.22-1.25	12.2-12.5	≥899	≥11.3	≥1114	≥14	287-310	36-39	100
  N40M	1.25-1.28	12.5-12.8	≥923	≥11.6	≥1114	≥14	302-326	38-41	100
  N42M	1.28-1.32	12.8-13.2	≥955	≥12	≥1114	≥14	318-342	40-43	100
  N45M	1.32-1.38	13.2-13.8	≥955	≥12.5	≥1114	≥14	342-366	43-46	100
  N48M	1.37-1.43	13.7-14.3	≥1027	≥12.9	≥1114	≥14	366-390	46-49	100
  N50M	1.40-1.45	14.0-14.5	≥1033	≥13	≥1114	≥14	382-406	48-51	100
  N35H	1.17-1.22	11.7-12.2	≥868	≥10.9	≥1353	≥17	263-287	33-36	120
  N38H	1.22-1.25	12.2-12.5	≥899	≥11.3	≥1353	≥ 17	287-310	36-39	120
  N40H	1.25-1.28	12.5-12.8	≥923	≥11.6	≥1353	≥17	302-326	38-41	120
  N42H	1.28-1.32	12.8-13.2	≥955	≥12	≥1353	≥17	318-342	40-43	120
  N45H	1.32-1.36	13.2-13.6	≥963	≥12.1	≥1353	≥ 17	326-358	43-46	120
  N48H	1.37-1.43	13.7-14.3	≥995	≥12.5	≥1353	≥17	366-390	46-49	120
  N35SH	1.17-1.22	11.7-12.2	≥876	≥11	≥1592	≥20	263-287	33-36	150
  N38SH	1.22-1.25	12.2-12.5	≥907	≥11.4	≥1592	≥20	287-310	36-39	150
  N40SH	1.25-1.28	12.5-12.8	≥939	≥11.8	≥1592	≥20	302-326	38-41	150
  N42SH	1.28-1.32	12.8-13.2	≥987	≥12.4	≥1592	≥20	318-342	40-43	150
  N45SH	1.32-1.38	13.2-13.8	≥1003	≥12.6	≥1592	≥20	342-366	43-46	150
  N28UH	1.04-108	10.4-10.8	≥764	≥9.6	≥1990	≥25	207-231	26-29	180
  N30UH	1.08-1.13	10.8-11.3	≥812	≥10.2	≥1990	≥25	223-247	28-31	180
  N33UH	1.13-1.17	11.3-11.7	≥852	≥10.7	≥1990	≥25	247-271	31-34	180
  N35UH	1.17-1.22	11.7-12.2	≥860	≥10.8	≥1990	≥25	263-287	33-36	180
  N38UH	1.22-1.25	12.2-12.5	≥876	≥11	≥1990	≥25	287-310	36-39	180
  N40UH	1.25-1.28	12.5-12.8	≥899	≥11.3	≥1990	≥25	302-326	38-41	180
  N42UH	1.28-1.32	12.8-13.2	≥899	≥11.3	≥1990	≥25	318-342	40-43	180
  N28EH	1.04-1.08	10.4-10.8	≥780	≥9.8	≥2388	≥30	207-231	26-29	200
  N30EH	1.08-1.13	10.8-11.3	≥812	≥10.2	≥2388	≥30	223-247	28-31	200
  N33EH	1.13-1.17	11.3-11.7	≥836	≥10.5	≥2388	≥30	247-271	31-34	200
  N35EH	1.17-1.22	11.7-12.2	≥876	≥11	≥2388	≥30	263-287	33-36	200
  N38EH	1.22-1.25	12.2-12.5	≥899	≥11.3	≥2388	≥30	287-310	36-39	200
  N40EH	1.25-1.28	12.5-12.8	≥899	≥11.3	≥2388	≥30	302-326	38-41	200
  N28AH	1.04-1.08	10.4-10.8	≥787	≥9.9	≥2624	≥33	207-231	26-29	230
  N30AH	1.08-1.13	10.8-11.3	≥819	≥10.3	≥2624	≥33	223-247	28-31	230
  N33AH	1.13-1.17	11.3-11.7	≥843	≥10.6	≥2624	≥33	247-271	31-34	230
  N35AH	1.17-1.22	11.7-12.2	≥876	≥11	≥2624	≥33	263-287	33-36	230
  N38AH	1.22-1.25	12.2-12.5	≥899	≥11.3	≥2624	≥33	287-310	36-39	230

• Mateirial : NDFEB MAGNET
  Grade: N35
  SIZE: D10X3 MM
  Coating: CHROME PLATED

• Magnetic Properties of Neodymium Magnets
  Grade	Residual Induction	Coercive Force	Intrinsic Coercive Force	Maximum Energy Product	Maximum Working Temperature
  	Br	Hcb	Hcj	(BH)max	Tw
  	mT	kA/m	kA/m	kJ/m3
  	[kGs]	[kOe]	[kOe]	[MGOe]
  N35	1170-1220	≥868	≥955	263-287	80°
  	[11.7-12.2]	[≥10.9]	[≥12]	[33-36]
  N38	1220-1250	≥899	≥955	287-310	80°
  	[12.2-12.5]	[≥11.3]	[≥12]	[36-39]
  N40	1250-1280	≥907	≥955	302-326	80°
  	[12.5-12.8]	[≥11.4]	[≥12]	[38-41]
  N42	1280-1320	≥915	≥955	318-342	80°
  	[12.8-13.2]	[≥11.5]	[≥12]	[40-43]
  N45	1320-1380	≥923	≥955	342-366	80°
  	[13.2-13.8]	[≥11.6]	[≥12]	[43-46]
  N48	1380-1420	≥923	≥955	366-390	80°
  	[13.8-14.2]	[≥11.6]	[≥12]	[46-49]
  N50	1400-1450	≥796	≥876	382-406	80°
  	[14.0-14.5]	[≥10.0]	[≥11]	[48-51]
  N52	1430-1480	≥796	≥876	398-422	80°
  	[14.3-14.8]	[≥10.0]	[≥11]	[50-53]
  30M	1080-1130	≥805	≥1114	223-247	100°
  	[10.8-11.3]	[≥10.1]	[≥14]	[28-31]
  33M	1130-1170	≥836	≥1114	247-263	100°
  	[11.3-11.7]	[≥10.5]	[≥14]	[31-33]
  35M	1170-1220	≥868	≥1114	263-287	100°
  	[11.7-12.2]	[≥10.9]	[≥14]	[33-36]
  38M	1220-1250	≥899	≥1114	287-310	100°
  	[12.2-12.5]	[≥11.3]	[≥14]	[36-39]
  40M	1250-1280	≥923	≥1114	302-326	100°
  	[12.5-12.8]	[≥11.6]	[≥14]	[38-41]
  42M	1280-1320	≥955	≥1114	318-342	100°
  	[12.8-13.2]	[≥12.0]	[≥14]	[40-43]
  45M	1320-1380	≥995	≥1114	342-366	100°
  	[13.2-13.8]	[≥12.5]	[≥14]	[43-46]
  48M	1370-1430	≥1027	≥1114	366-390	100°
  	[13.7-14.3]	[≥12.9]	[≥14]	[46-49]
  50M	1400-1450	≥1033	≥1114	382-406	100°
  	[14.0-14.5]	[≥13.0]	[≥14]	[48-51]
  35H	1170-1220	≥868	≥1353	263-287	120°
  	[11.7-12.2]	[≥10.9]	[≥17]	[33-36]
  38H	1220-1250	≥899	≥1353	287-310	120°
  	[12.2-12.5]	[≥11.3]	[≥17]	[36-39]
  40H	1250-1280	≥923	≥1353	302-326	120°
  	[12.5-12.8]	[≥11.6]	[≥17]	[38-41]
  42H	1280-1320	≥955	≥1353	318-342	120°
  	[12.8-13.2]	[≥12.0]	[≥17]	[40-43]
  45H	1320-1360	≥963	≥1353	342-366	120°
  	[13.2-13.6]	[≥12.1]	[≥17]	[43-46]
  48H	1370-1430	≥995	≥1353	366-390	120°
  	[13.7-14.3]	[≥12.5]	[≥17]	[46-49]
  35SH	1170-1220	≥876	≥1592	263-287	150°
  	[11.7-12.2]	[≥11.0]	[≥20]	[33-36]
  38SH	1220-1250	≥907	≥1592	287-310	150°
  	[12.2-12.5]	[≥11.4]	[≥20]	[36-39]
  40SH	1250-1280	≥939	≥1592	302-326	150°
  	[12.5-12.8]	[≥11.8]	[≥20]	[38-41]
  42SH	1280-1320	≥987	≥1592	318-342	150°
  	[12.8-13.2]	[≥12.4]	[≥20]	[40-43]
  45SH	1320-1380	≥1003	≥1592	342-366	150°
  	[13.2-13.8]	[≥12.6]	[≥20]	[43-46]
  28UH	1040-1080	≥764	≥1990	207-231	180°
  	[10.4-10.8]	[≥9.6]	[≥25]	[26-29]
  30UH	1080-1130	≥812	≥1990	223-247	180°
  	[10.8-11.3]	[≥10.2]	[≥25]	[28-31]
  33UH	1130-1170	≥852	≥1990	247-271	180°
  	[11.3-11.7]	[≥10.7]	[≥25]	[31-34]
  35UH	1170-1220	≥860	≥1990	263-287	180°
  	[11.7-12.2]	[≥10.8]	[≥25]	[33-36]
  38UH	1220-1250	≥876	≥1990	287-310	180°
  	[12.2-12.5]	[≥11.0]	[≥25]	[36-39]
  40UH	1250-1280	≥899	≥1990	302-326	180°
  	[12.5-12.8]	[≥11.3]	[≥25]	[38-41]
  28EH	1040-1080	≥780	≥2388	207-231	200°
  	[10.4-10.8]	[≥9.8]	[≥30]	[26-29]
  30EH	1080-1130	≥812	≥2388	223-247	200°
  	[10.8-11.3]	[≥10.2]	[≥30]	[28-31]
  33EH	1130-1170	≥876	≥2388	247-271	200°
  	[11.3-11.7]	[≥10.5]	[≥30]	[31-34]
  35EH	1170-1220	≥876	≥2388	263-287	200°
  	[11.7-12.2]	[≥11.0]	[≥30]	[33-36]
  38EH	1220-1250	≥899	≥2388	287-310	200°
  	[12.2-12.5]	[≥11.3]	[≥30]	[36-39]
  28AH	1040-1080	≥787	≥2624	207-231	220°
  	[10.4-10.8]	[≥9.9]	[≥33]	[26-29]
  30AH	1080-1130	≥819	≥2624	223-247	220°
  	[10.8-11.3]	[≥10.3]	[≥33]	[28-31]
  33AH	1130-1170	≥843	≥2624	247-271	220°
  	[11.3-11.7]	[≥10.6]	[≥33]	[31-34]

• 
  The Physical Properties of Neodymium Magnets
  
  

• Parameters	Units	Indicators
  Density	g/cm³	≥7.3
  Home temperature	℃	310-340
  BrReversible temperature coefficient	℃/%	-0.100~-0.130
  HcjReversible temperature coefficient	℃/%	0.40~0.70
  Compressive strength	N/mm2	1050
  Bending strength	N/mm2	250
  Tensile strength	N/mm2	80
  Webster Hardness		600
  Coefficient of thermal expansion(20 to 200℃)	10-6/k	∥5⊥-1.5
  Specific heat	J/(Kg.K)	460
  Thermal conductivity	W/(m.K)	9
  Resistivity	μΩ.cm	150

• 
  The Surface Coatings of Neodymium Magnets
  
  

• Surface Coating	Coating Method	Coating thickness(m)	Coating Color	Coating features
  Nickel	plating	≥5	Yellow	Corrosion resistance strong,with outstanding resistance to high temperature and humidity capabilities
  zinc	plating	≥5	Silvery white	Has strong corrosion resistance,anti-salt spray test ability .
  gold	plating	≥5	gold	Has outstanding resistance to high temperature capability,corrosion resistance,good resistance to color change ablity
  Ni-Cu-Ni	plating	15-30	sliver	strong corrosion resistance
  Epoxy	Electrophoresis	15-20	Black/grey	strong corrosion resistance,outstanding resistance to salt spray,strong resistance to high temperature, high humidity capacity