RU2069913C1 - Multilayer amorphous magnetically soft coating - Google Patents

Abstract

FIELD: electronics. SUBSTANCE: cobalt-iron-phosphorus coating is deposited in layers into multilayer structure in which layers of cobalt-iron-phosphorus are separated by interlayers of copper with thickness 5.0-15.0 A. EFFECT: facilitated coating process. 1 tbl

Description

 The invention relates to soft magnetic materials based on cobalt used in a variety of magnetic microelectronic devices. In particular, the proposed invention is promising for use in magnetic integrated recording and reading heads, microtransformers, and other similar devices where low-coercive and at the same time thermostable materials are needed.

 The main parameter of the working soft magnetic material in the above devices is the temperature of the onset of its crystallization (Tn.k). Exceeding this temperature leads to degradation of the performance of the device in which the soft magnetic material is used. Thus Tn.k. determines the temperature range of the stable operation of the device.

Currently, the most widely known amorphous magnetically soft metal-metalloid coatings based on elements of the iron group (Co, Fe and Ni) with phosphorus (1), obtained by chemical and electrolytic deposition. Depending on the composition Tn.k. these alloys is 220-240 ^o C.

 For more stable operation of devices that use amorphous low-coercive coatings, materials with higher crystallization temperatures are needed.

 An object of the present invention is to provide an amorphous soft magnetic coating with an increased crystallization temperature.

и с разделяющими немагнитными прослойками меди толщиной 5-15

Многослойные структуры Co-Fe-P/Cи осаждают из электролита состава, г/л:
CoSO₄•7H₂O 150-170
CoCl₂•6H₂O 5-15
FeSO₄ •7H₂O 25-70
H₃BO₃ 20-40
Na₃C₆H₅O₇•5,5H₂O 5-15
Cахарин 0,4-1,2
NaH₂PO₂•2H₂ 10-30
CuSO₄•7H₂O 1-2
при рН 1,4-1,6, Т 60-85^oС.To achieve this goal, an amorphous soft magnetic coating is proposed, containing, by weight. iron 4-7.9, phosphorus 7.6-12.0, the rest, which, in order to increase the crystallization temperature, is multilayer with layer thicknesses 10-50

and with separating non-magnetic layers of copper with a thickness of 5-15

The multilayer structures Co-Fe-P / C and precipitate from the electrolyte composition, g / l:
CoSO ₄ • 7H ₂ O 150-170
CoCl ₂ • 6H ₂ O 5-15
FeSO ₄ • 7H ₂ O 25-70
H ₃ BO ₃ 20-40
Na ₃ C ₆ H ₅ O ₇ • 5.5H ₂ O 5-15
Saccharin 0.4-1.2
NaH ₂ PO ₂ • 2H ₂ 10-30
CuSO ₄ • 7H ₂ O 1-2
at a pH of 1.4-1.6, T 60-85 ^o C.

The current density of the deposition of amorphous Co-Fe-P layers Dc ₁ 25-35 mA / cm ² when the pulse duration t ₁ 1-3 s. The current density of the deposition of copper layers DK ₂ 0.4-0.6 mA / cm ² with a duration of t ₂ 2-7 s. The number of applied rectangular pulses and, accordingly, the number of layers in the resulting multilayer structure N 50.

 Common features of the known technical solution and the claimed is that the composition of the amorphous low-coercive coating includes cobalt, iron and phosphorus.

в многослойную структуру, в которой слои указанного аморфного сплава разделены слоями меди толщиной 5-15

Положительный эффект достигается за счет получения мультислойной магнитной аморфной структуры Co-Fe-P/Cи, в которой сверхтонкие прослойки меди препятствуют диффузионным процессам кристаллизации в аморфных слоях Co-Fe-P из-за того, что медь практически не растворяется в сплавах на основе кобальта и железа.Distinctive features is that the amorphous soft magnetic coating cobalt-iron-phosphorus is included in thin layers with a thickness of 10-50

in a multilayer structure in which the layers of the specified amorphous alloy are separated by layers of copper 5-15 thick

A positive effect is achieved by obtaining a multilayer magnetic amorphous structure of Co-Fe-P / Ci, in which ultrathin layers of copper interfere with diffusion crystallization processes in amorphous Co-Fe-P layers due to the fact that copper practically does not dissolve in cobalt-based alloys and iron.

The above principle of increasing the crystallization temperature of an amorphous magnetically soft cobalt-iron-phosphorus coating by creating a Co-Fe-P / C multilayer magnetic structure with ultrathin alternating layers of the amorphous Co-Fe-P alloy and copper layers was previously unknown and is a significant difference. since on single-layer amorphous metal-metalloid coatings based on elements of the iron group with phosphorus it is impossible to achieve the stated goal of increasing the crystallization temperature of the amorphous magnetically soft Co-Fe-P alloy less than 330-350 ^o C.

The inventive multilayer magnetic amorphous coating is deposited from an electrolyte, which is prepared as follows: simultaneously dissolve CoSO ₄ • 7H ₂ O, CoCl ₂ • 6H ₂ O, FeSO ₄ • 7H ₂ O, NaH ₂ PO ₂ • 2H ₂ O and CuSO ₄ • 7H ₂ O in distilled water at 80 ^o With vigorous stirring. H ₃ BO ₃ and Na ₃ C ₆ H ₅ O ₇ • 5.5H ₂ O are dissolved in separate portions. Saccharin is also dissolved in a separate volume with the addition of a few drops of NaOH. After cooling, all prepared portions of the solutions are drained and the volume of electrolyte is adjusted to the volume corresponding to the required concentration of components by adding distilled water. Next, the pH of the electrolyte was adjusted to the desired value with a 10% solution of H ₂ SO ₄ and a 25% solution of NH ₄ OH and filtered using blue ribbon filters. The anode is used cobalt. The deposition is carried out on copper or chemically precipitated nickel phosphide in a thermostatic bath using a pulsed programmable power source.

 Example.

Weighed portions of CoSO ₄ • 7H ₂ O, CoCl ₂ • 6H ₂ O, FeSO ₄ • 7H ₂ O, NaH ₂ PO ₂ • 2H ₂ O and CuSO ₄ • 7H ₂ O in quantities of 160, 10, 50, 20 and 1, respectively 5 g and dissolved in 500 ml of distilled water at 80 ^o With vigorous stirring. Samples of H ₃ BO ₃ and Na ₃ C ₆ H ₅ O ₇ • 5.5H ₂ O in an amount of 30 and 10 g, respectively, are dissolved in ≈ 50 ml in separate portions of distilled water. Saccharin in an amount of 0.8 g is dissolved in ≈ 10 ml of H ₂ O with the addition of small amounts of NaOH. After cooling, all prepared portions are poured together and the electrolysis volume is adjusted to 1 liter. Next, the pH of the electrolyte was adjusted to 1.5 with a 10% solution of H ₂ SO ₄ and 25% NH ₄ OH and filtered. The deposition is carried out in a thermostatic bath at T 70 ^o C, DK ₁ 30 mA / cm ² , DK ₂ 0.5 mA / cm ² , t ₁ 2 s, t ₂ 5 s. The number of layers is N 50. The amorphous structure of the obtained precipitate is confirmed by the characteristic “halo” in the X-ray diffraction patterns recorded using the DRON-3M apparatus. The layer thickness in multilayer structures was determined using the method of Auger spectroscopy, as well as by calculation. The temperature at which crystallization begins Tn. K. determined from measurements of the dependence of the magnetization of the obtained structures on temperature using a vibration magnetometer "PARC-4500", amounted to 350 ^o C. Moreover, the coercive force Нс, determined by the induction method, was 1, 2 E.

 The examples presented in the table indicate that the optimal, from the point of view of using them as an amorphous soft magnetic coating, are the multilayer structures shown in examples 1 to 3.

 To ensure sufficiently low coercive forces of amorphous films, we used the same coating compositions (respectively, the same electrolyte compositions and deposition modes) as in the prototype. The difference is that we obtained these amorphous alloys in the form of very thin layers, alternating with layers of copper.

(примеры 4, 5 и 7) нецелесообразно из-за уменьшения при этом диффузионных затруднений процесса кристаллизации аморфных слоев и таким образом уменьшения температуры их кристаллизации. При толщинах d_Co-Fe-P менее 10

(примеры 4 и 6) слои, по-видимому, также являются несплошными, а в их состав входит большое количество меди, что приводит к увеличению коэрцитивной силы покрытий.At times of deposition of copper layers t ₂ less than 2 s, their thickness d _{Cu is} very small (examples 4 and 8) and is most likely non-continuous. Therefore, in this case, the obtained structure is actually single-layer with the temperature of crystallization initiation T. typical for single layer formulations. The use of large thicknesses of copper layers with pulse durations of copper deposition t ₂ ≥ 10 s (examples 5 and 3) is impractical due to the relatively long deposition time of the multilayer structure, as well as some increase in Hc. The use of Co-Fe-P layer thicknesses greater than 50

(examples 4, 5 and 7) is impractical due to the reduction of diffusion difficulties in the process of crystallization of amorphous layers and thus a decrease in the temperature of their crystallization. With thicknesses d _Co-Fe-P less than 10

(examples 4 and 6), the layers are also apparently discontinuous, and their composition includes a large amount of copper, which leads to an increase in the coercive force of the coatings.

Thus, the claimed invention allows to obtain multilayer amorphous magnetic coating composition, wt. Fe 4-7.9, P 7.6-12.0, Co the rest with a temperature of crystallization onset is significant, more than 100 ^o With, exceeding the crystallization temperature of known analogues. Other characteristics of the coercive force H _c and saturation magnetization M _s correspond to the requirements for devices that use amorphous soft magnetic coatings.

The invention has the following technical and economic effect. By increasing the crystallization onset temperature by 100 ^{° C.} , the temperature range for maintaining the operability of the device in which this multilayer amorphous magnetic coating is expanded is also expanded. For example, a magnetic head (MG) with an amorphous multilayer Co-Fe-P / Ci structure will remain operational up to 330-350 ^o C. In this case, the economic effect per MG is approximately equal to its cost (300 rubles).

Claims (1)

Amorphous soft magnetic coating based on the cobalt-iron-phosphorus system, characterized in that, in order to improve performance by increasing the crystallization temperature, it is multilayer with a thickness of the cobalt-iron-phosphorus system 10 50

and with separating non-magnetic layers of copper with a thickness of 5 15

.

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