CA1160869A - Low magnetostriction amorphous metal alloys - Google Patents

Abstract

ABSTRACT
Cobalt rich amorphous metal alloys have a value of magnetostriction of about -6 x 10-6 to +4 x 10-6 and a saturation induction of about 0.1 to 1.0T. The alloys, especially suited for soft magnetic applications, have the formula (Co1-xmx)100-b(B1-yYy)b, where T is at least one of Cr and V, Y is at least one of carbon and silicon, B is boron, x ranges from about .05 to .25, y ranges from about 0 to .75 and b ranges from about 14 to 28.

Description

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DESCRI PTI ON
LO~ AGNETOSTRICTION AMORPHOUS METAL ALLOYS
BACKGROUND OF THE INVENTION
1. Field of the Invention This invention relates to amorphous metal alloys and, more particularly, to cobalt rich amorphous metal alloys that include certain transition metal and metalloid elements.

2. Description of the Prior Art There are three physical parameters which can inhibit the easy magnetization and demagnetization of magnetic materials: strong anisotropy, non-zero mag-netostriction and, at high frequencies, low resis-tivity~ Metallic glasses generally show resistivities greater than 100 micro ohm cm, whereas crystalline and polycrystalline magnetic metals generally show resis-tivities below 50 micro ohm cm. Also, because of theirrandomly disordered str~ctures, metallic glasses are typically isotropic in their physical properties, in-cluding their magnetization. Because of these two characteristics, metallic glasses have an initial ad-vantage over conventionaI magnetic metals. However, metallic glasses do not generally show zero magneto-striction. When zero magnetostriction glasses can be found they are generally good soft magnetic metals tR.C. O'Handley, B.A, Nesbitt, and L.I. Mendelsohn, IEEE Trans Mag-12, p. 942, 1976, U~S. Patents Nos.
4,038,073 and 4,150,981), because they satisfy the three approved criteria. For this reason, interest in ,~
` ' zero magnetostriction glasses has been intense as indi-cated by the many publications on low magnetostriction metallic glasses (A W. Simpson and W.G. Clements, IEEE
Trans Mag-11, p. 1338, 1975; N. Tsuya, K.I. Arai, Y.
Shiraga and T. Masumoto, Phys. Lett. A51, p. 121, 1975;
H.A. Brooks, Jour. Appl. Phys. 47, p. 334, 1975j T.
- Egami, P.J. Flanders and C.D. Graham, Jr., Appl. Phys.
Lett. 26, p. 128, 1975 and AIP Conf. Proc. No. 24, p.
697, 1975; R.C. Sherwood, E.M. Gyorgy, H.S. Chenr S.D.
Ferris, G. Norman and H.J. Leamy, ~IP Conf. Proc. No.
24, p. 745, 1975; H. Fujimori, K.I. Arai, H. Shiraga, ~.
Yamada, T. Masumoto and ~. Tsuya, Japan, Jour. Appl.
Phys. 15, p. 705, 1976; L. Kraus and J. Schneider, phys. stat. sol. a39, p. ~1~1, 1977; R.C. O'l~andley in Amorphous Magnetism, edited by R. Levy and R.
~asegawa (Plenum Press, New York 1977), p. 379; R.C.
O'EIandley, Solid State Communications 21, p. 1119, 1977;
R.C. O'Handley, Solid State Communications 22, p. 458, 1977; R.C. O'Handley, Ph~s. ~ev. 18, p. 930, 1978; H.S.
Chen, E.M. Gyorgy, H.J. Leamy and R.C. Sherwood, U.S.
Patent No. 4,056,411, Nov. 1, 1977).
The existence of a zero in the magnetostric-tion of Co-Mn-B glasses has ~een observed by H. Hilt-zinger of Vacuumschmeltze A.~ anau, Germany.
Reference to Co-rich glasses containing 6 atom percent of Cr is made by N. Heiman, R.D. Hempstead and N. Kazama in Journal of Applied Physics, Vol. 49, p.
5663, 1978. Their interest was in improving the corrosion resistance of Co-B thin films. No reference to magnetostriction is made in that article.
Saturation moments and Curie temperatures of Co80 TXPloBlo glasses (T = Mn, Cr, or V) were recently reported b~7 T. Mizoguchi in the Supplement to the Scien-tific Reports of RITU (Research Institutes of Tonoku University), A June 1978r p. 117. No reference to their magnetostrictive properties was reported.
In Journal of Applied Physics, Vol. 50, p. 7597, 1979, S. Ohnuma and T. Masumoto outline ~6(;~ 9 their studies of magnetization and magnetostriction in Co-Pe-B-Si glasses with light transition metal (Mn, Cr, V, W, Ta, Mo and Nb) substitutions. They show that the coercivity decreases and the effective permeability increases in the composition range near zero magneto-striction.
New applications requiring improved soft zero-magnetic materials that are easily fabricated and have excellent stability have necessitated efforts to develop ln further specific compositions.
SUM~1~RY OF TE~E INVENTIOil The present invention provides lo~ magneto-striction and zero magnetostriction glassy alloys that are easy to fabricate and thermally stable. The alloys are at least about 50 percent glassy and consist essentially of compositions defined by the formula:
( l-xTx)l00_b(Bl_y~y)b~ where T is at least one of Cr and V, Y is at least one of carbon and silicon, B is boron, x ranges from about .05 to .25, y ranges from about 0 to .75, and b ranges from about 14 to 28 atom percent. The alloys of the invention have a value of magnetostriction ranging from about -6 x 10 6 to 4 x 10 6 and a saturation induction of about 0.2 to 1.0T.
In addition, the invention provides cobalt-iron-nickel base and nickel-rich magnetic alloys that are easily fabricated and thermally stable. The cobalt-iron-nickel base alloys are at least 50 percent glassy and consist essentially of compositions defined by the formula: (Col y zFexNiyTg)loo-b(Bl-w w)b' T is at least one of ~n, Cr, V, Ti, Mo, N~ and W, M is at least one of Si, P, C and Ge, B is boron, x ranges from about .05 to .25l y ranges from about .05 to .80, z ranges from about 0 to .25, b ranges from about 12 to 30 atom percent, w ranges up to .75 when M is Si or Ge and u~ to .5 when M is C or P. These alloys have a value of magnetostriction of about -7 x 10 ~ and +5 x 10 6 and a saturation induction of about 0.2 to 1.4T. The nickel-rich alloys are at least 50 percent glassy and consist essentially of compositions defined by the formula:
(Ni.5Co.5_xTx)l~0_bBb, where T is at least one of Mn, Cr and V, B is at least one of B, Si, P, C and Ge, x is less than 0.25, and b ranges from 17 to 22 atom percent.
The nickel-rich alloys have a value of magnetostriction of about -8 x 10 6 to +2 x 10 6 and a saturation induc-tion of about 0.3 to 0.8 T.
BRIEF DESCRIPTION OF THE DRAWINGS
The invention will be more fully understood and further advantages will become apparent when refer-ence is made to the following detailed description of the preferred embodiments of the invention and the accompanying drawings, in which Figure 1 is a graph showing saturation magne-tization for compositions defined by the formulaCo80 XTxB20, where T is at least one of Fe, Mn, Cr and V
and x ranges up to about 16 atom percent;
Figure 2 is a graph showing Curie temperatures of compositions for which T is below the crystalliza-2n tion temperature Tx;
Figure 3 is a graph showing the relationshipsbetween saturation maynetostricl:ion and composition for selected alloys of thle invention;
Figure 4 is a graph showing the relationships between temperature and magnetostriction values for selected alloys of the invention;
Figure 5 shows the cobalt-rich corners of triangular diagrams for compositions defined by the formula (Col_x_yFe~Ty)8oB2o~ where T is at least one of V, Cr, Mn, Fe, Co and Ni; and Figure 6 is a triangular Fe-Co-Ni diagram showing regions of positive and negative magneto-striction, the dotted line isolating therefrom the region of nickel-rich compositions wherein amorphous metals are difficult to form and thermally unstable.
DESCRIPTION O~ T~E PREFERRE~ E~lBODI~ENTS

In accordance with the invention, there is provided a magnetic alloy that is at least 50 percent glassy and consists essentially of the composition:
(Col-xTx)loo-btBl-yyy)bl where T is at least one of chromium and vanadium, Y is at least one of carbon and silicon, x ranges from about .05 to .25, y ranges from about O to .75, and b ranges from about 14 to 23 atom percent. The glassy alloy has a value of magnetostric-tion of abcut -6 x 10 to 4 x 10 and a saturation induction of about 0.2 to l.OT.
The purity of the above composition is that found in normal commercial practice. However, it will be appreciated that the alloys of the invention may contain, hased on total composition, up to about 5 atom percent of at least one other transition metal element, such as Fe, Co, Ni, Cu, Zn, Mn, Cr, V, Ti, Zr, ~b, Ta, Mo, W, Ru, r~h and Pd, and up to about 2 atom percent based on total composition of at least one other metal-loid element, such as B, Cr Si, P, Ge, Al, N, O and S, without significantly degrading the desirable magnetic properties of these glassy alloys.
The amorphous alloys of the invention can be formed by cooling a melt o the composition at a rate of at least about 105C/sec. ~ variety of techniques are available, as is now well-known in the art, for fabricating splat-quenched foils and rapid-quenched continuous ribbons, wire, sheet, etc. Typically, a particular composition is selected, powders of the requisite elements (or of materials that decompose to form the elements, such as nickel-borides, etc.) in the desired proportions are melted and hornogenized, and the molten alloy is rapidly quenched either on a chill surface, such as a rotating cooled cylinder, or in a suitable fluid medium, such as a chilled brine solution. The amorphous alloys may be formed in air.
However, superior mechanical properties are achieved by formin~ these amorp~ous alloys in a partial vacuum with absolute pressure less than about 5.5 cm of Hg, and preferably about 100 ~m to 1 cm of flg, as disclosed ~.6~

in U.S. Patent No. 4,154,283 to Ray et al.
The amorphous metal alloys are at least 50 percent amorphous, and preferably at least 80 percent amorphous, as measured by X-ray diffraction. However, a substantial degree of amorphousness approaching 100 per-cent amorphous is obtained by forming these amorphous metal alloys in a partial vacuum. Ductility is thereby improved, and such alloys possessing a substantial degree of amorphousness are accordingly preferred.
Ribbons of these alloys find use in soft magnetic applications and in applications requiring low magnetostriction, high thermal stability (e.g., stable up to about 100C) and excellent fabricability.
The following example is presented to provide a more complete understanding of the invention. The specific techniques, conditions, materials, proportions and reported data set forth to illustrate the principles and practice of the invention are exemplary and should not be construed as limiting the scope of the invention.
E~.AMPL~
An alloy melt of ~nown composition was rapidly ~uenched to form non-crystalline ribbons, presumably of the same composition as the melt~ The ribbons, typi-cally 40 micrometers (~m) by 2 mm in cross section, were cut into squares for vibration-sample magnetometer measurements of specific magnetization ~(4.2K, 9 ~Oe) and ~(T, 9 KOe) with 295 K < T < Tx~ the crystallization temperature. Curie temperatures were obtained ~rom the inflection points in the ~(T, 9 KOe) curves.
The magnetostriction measurements were made in fields up to 4 KOe with metal foil strain gauges (as reported in more detail by R.C. O'~andley in Solid State Communications, Vol. 22, p. 485, 1977). The accuracy of these measurements is considered to be within 10 percent of full strain and their strain sensitivity is on the order of 10 Composition variations of the room temperature specific saturation magentizations ~(295 K, 9 ~Oe) as 6~B~3~ .

functions of composition x for Co80_xTxB20 ~T Fe, M , Cr, V) glasses are shown in Figure 1. The trends in Figure 1 reflect the variations of both the saturation moments nB and the Curie temperatures TC of these alloys.
The Curie temperatures of Co rich glasses are generally well above the temperatures for crystalliza-tion Tx but fall below T for sufficiently large addi-tions of Cr or V (Figure 2).
In order to be useful in magnetic devices, materials should sho~ appreciable magnetization. Com-mercial zero ~,agnetostriction crystalline metallic alloys of the class exemplified by Permalloy ((Ni82Fel8)1_xXx -~ith x = Mo or Cu and x < ~04) have saturation inductions Bs = H + 4 ~ Ms = 4~ Ms of about 0.6 to 0.8 tesla (6 to 8 kGauss). The specific magne-tizations in Figure 1 can be converted to tesla by mul-tiplying by the mass density times 4 ~/10,000. Densi-ties for the glasses studied here can be estimated froJn the measured densities for Co80B20, Fe~OB20 and Co70Fe1OB20 glasses and the known densities of crystal-line Co, Fe, Mn, Cr and V.
Defining Px to be the mass density of the crystalline material X and pg to be that of the glassy material x80s20, the ratios of the measured quantities Pg/PX were found to be 0.92 and 0.94 for Co80B20 and Fe80B2n glasses. A similar trend holds for the hypo-thetical X80B20 glasses listed in Table I. The estimated densities of X80s20 (~ = Mn, Cr, V) glasses are also set forth in Table I. The densities of CO70XloB20 glasses were calculated by linearly colnbining the densities of Co80B2o and ~80B20 Th obtained for Co70Fe1OB20 is less than 1 percent larger than the ~easured density for that glass.

TA~LE I
Densities and Saturation Inductions for C70XlOB20 Glasses -Crystalline X 80 20 Glass Co70XlOB20 Glass Px Pp /p ~aturation Density Den~ity g x ~ensity Induction X (gm/cm ) (gm/cm3) (gm/cm3) (tesla) Co 8.90 8.22 (a) .92 8.22 (a) 1.14 (a) Fe 7.86 7.41 (a) .94 8.12 (b) 1.25 (c) 8.06 (a) 1.24 (a) Mn 7.43 7.06 (b) .95 8.06 (b) 1.11 (c) Cr 7.19 6.90 (b) .96 8.04 (b) 0.59 (c) V 6.00 5.82 (b) .97 7~92 (b) 0.43 (c) (a) measured (b) estimated (c) rneasured specific magnetization, estimated density.
In Figure 3, there is shown the effects of Fe, Mn, Cr and V substitutions on the saturation magneto-striction of Co80B20 glass. As is the case with the Pe substitutions for Co disclosed by ~.S. Patent No~
4,038,073 to O'Handley et al., the lighter transition metals cause ~ to increase through zero, positive below Tc for Mn and Cr substitutions and go to zero for V sub-stitutions. In the case of Co66V14B20 glass, Tc =
300 ~ (Fig. 2). Thus, the room temperature magneto-striction is zero probably because of the low Tc.
Co80 XVxB20 glasses with x > 14 may show positive mag-netostriction at 4.2 K (see Fig. 4). These Co~Mn-B and Co-Cr-B glasses are, therefore, non-magnetostrictive allovs. Co74Fe6~20 and related glasses are non-magneto-strictive alloys that have approximately two tinles the magnetization of the permalloys for which ~= 0.
Co71Mn9B20 glass is in the same category, with ~= 0 and ~(295 K = 111 e~u/gm (4 ~M = 11 k~auss).
The te~perature dependence of ~s is shown in Figure 4 for selected alloys. The si~n of ~s was ob-served to change in two of the glasses. Such compen-sation ternperatures have not previously been observedin metallic glasses. The vanadium containing glasses either become paramagnetic or they crystallize before any compensation can be realized. Thus, the negative magnetostriction glasses shown in Figure 3 may be used in applications requiring ~ = 0 at some elevated tem-perat~re (up to approximately 200C above room tempera-ture, which is not uncommon in man~7 electronic devices).
The new low magnetostriction metallic glasses disclosed herein ~Co-Cr-B and Co-V-B) show relatively low 4~Ms (Fig. l). As a result, their utility is limited to applications requiring superior mechanical properties or improved corrosion resistance relative to permalloys or other ~ = 0 crystalline or non-crystal-line materials.
Co-rich glass compositions with positive and negative magnetostriction can be added linearly to ~ive zero magnetostriction. For eY.ample, ~s for Co70Fel0B20 and Co80B20 glasses are +4 and -4 x l0 6, respectively.
~ 50-50 percent mixture of these glasses gives Co75Fe5~20 which c1Oes in fact show ~s = (O'Handley et al., IEE~ Trans Mag-l~, p. 942, 1976). Similarl~, for 40Ni40~40 ~s = ~7 x l0 6 while for Fe80B20 ~s = 32 x l0 6. ~ linear rnixture having ~ = 0 ( 80 20) (C40 i40~20) Co33~i33Fel4B20 which is very close to the observed s 33.5 33.5 13 20 The rule of linear combination of opposing magnetostrictions (LCOM) has been applied to develop additional zero magnetostriction glasses from those measured and shown in Figure 3. Table II lists several such glasses and Fiyure 5 shows where they fall in the Co-rich corner of a trianyular co~position diagra~.
The lines connecting these newly developed ~s =
cor,lpositions closely follow the observations of Ohnu~a and Masumoto (cited above) for (Co Fe ~)78Bl4Si8 ~lasses (with ~' = Mn, Cr, V) despite the different metalloids used in the two cases.

TA~LE I I
Some ~ear-zero Magnetostriction Cobalt-rich Glasses Developed by the LCOM Method S C73Fe4.5Mn2.5 20 Co73Fe2Mn5B20 Co73Fe2 5Mn4~5 20 73 5 2 20 Co71Fe4.5Cr4.5B20 Co7oFe2 . 5Cr7 . 5B20 Co73Fe3.5V3.5B20 Co71Fe3V6B20 Co70 5Fe2.5V7 20 C72 3Fe4.3V3.4 20 70 5 5 20 Co69Mn5Cr6B20 cO66cr8v632o -rrhe magnetostriction of Co-rich glasses is small because of the near-cancellation of two indepen dent mechanisms for the magnetostriction, a positive two-ion interaction and a negative single-rn~i-ion term (O'Handley, Phys. Rev. B 18, p. 930, 1978). As a re-sult, the TM makeup for ~s = is nearly independent of TM/M ratio. That is, because ~s ~ 0 for (Co 94Fe 06)80B20, is nearly zero for other compositions (Co 94Fe 06)~0Q XBx such that 12 < x < 2~ atom percent An improvement on this approximation can be realized b~
taking into account the fact that the strength ~f the negative single-ion term varies linearly with the concentration of magnetic ions, i.e , at (100-x). The two-ion term should vary as the number o T~l pairs at short range. However, observed trends in Col00_xBx glasses (K. Narita, J. Yamasa~i, and H. Fukunaga, Jour.
Appl. Phys. Vol. 50, p. 7591, 1979 and J. Aboaf and E.
Klokholm, ICM Munich Sept. 1979 to appear in Jour.
Magnetism an~ l~lagnetic Materials), are ~est ~escribed by assuming the number of neares~ neigh~or T~ pairs to be independent of x. This i~plies that the nearest-neighbor coordination of cobalt atoms by cobalt atolns does not vary strongly with x. Thus the compositional dependence of magnetostriction in Co-rich glasses is well described at room temperature b~:
~s ~+ 6-8 x 10 - 10.2 x 10 x (100-x)/~0 where the 5 first term is the observed two-ion component of maynetostriction (independent of composition x) and the second is the single-ion component of magnetostric-tion (which varies linearly with the TM concentration).
Thus the magnetostriction becomes less negative as 3 10 metalloid content increases, the change in ~ being +0.13 x 10 6 per atom percent rnore metalloid.
Alternatively, the zero magnetostriction composition is shifted to ylasses richer in iron as 100-x increases, the shift being approximately +0.23 percent Fe per 15 1 percent decrease in x.
As a result, the Co-Fe-T ratios (T = Mn, Cr, V) for ~s = in Figure 5 hold approximately for other TM/M ratios in the glass-forming range 12 < x < 28 atom percent. A first order correction shifts the ~s =
20 lines toward Fe by approximately 1 percent for every 4 percent decrease in x Metalloid type has little effect on the magni-tude or sign of magnetostriction in Co-rich ylasses (C'~andley in Amorphous Magnetism eds. R. Levy and R.
~asegawa, Plenum Press 1977, p. 379). Hence, the com-positions in Table II and Figure 5 will still be of near-zero magnetostriction if B is replaced by P, C, Si or some combination of these metaloids.
The rule of linear combination of opposing magnetostrictions (LC~tM) can also be applied across the Co-Ni side of the Fe-Co-~i triangular ~aynetostriction dia~ram shown in Figure 6 (see also U.S. Patent No.
~,150,981 to O'EIandley). Table III sets forth some t~7pical near-zero magnetostriction compositions.

TABLE III
New Co-Ni ~ase Glassy ~lloys or ~ear-zero Magnetostriction Developed by LCOM Method.
Co66Mn9Ni5~20 C68 4Mn8.3Ni3.3~20 CoS3 71~il5 . 3Fes . sMn5 . 5B20 Co52Nil8Fe8Mn2B2o Co4lNi3oFe5Mil4B2o Ni45Co26 . 5Fe7 . 5MnlB20 Co58Nil2Fe6Mn4B 20 Co51Nil8Fe8Cr3B20 Co391~i30Cr6Fe5B20 Co56Nil2Fe6Cr6B20 Co5lNil8Fe9cr2E~2o Co40Ni3oFesvsB2o Co59l~il2Fe6V5B20 -Referring to Figure 6, a region of dif~icult to fabricate and relatively unstable glasses exists in the Ni-rich corner of the triangular Fe-Co-~li diagram.
Yet, glassy alloys of zero or low m~ynetostriction exist there with potential for various applications.
Ni-rich glasses are more easily made and are more stable if the "late" transition metal ~i is balanced to a certain extent by an "early" TM, e.g., ,Mn, Cr, V. ~xamples of such glasses include ~i50Mn30B20 r Ni60Cr20~20~ or Ni70V10 20 Based on the evidence of ~s = alloys set forth above and the known stabilizing effects of light TM's on Ni-rich glasses, new low ~,agnetostriction glasses rich in Ni have been developed in the region below or near the ~ = 0 line in Figure 8 (i.e., glasses initially showing ~ < 0) by the addition of Mn, Cr, and/or V. Thus, for example, (Co 2s~i 7s)80B20 can be rendered more fabricable and more stable in the glassy state, and its negative magnetostriction can be increased to near zero by substituting Mn, Cr or V for 8b9.

Co: (Ni 7sC~2s-xTX)80~20~
Having thus described the invention in rather full detail, it will be understood that such detail need not be strictly adhered to but that various changes and modifications may suggest the~selves to one skille~ in the art, all falling within the scope of the invention as defined by the subjoined claims.

Claims (2)

We claim:

1. A magnetic alloy that is at least about 50 percent glassy, having the formula (Co1-xTx)100-b(B1-yYy)b, where T is at least one of chromium and vanadium, Y is at least one of carbon, silicon, phosphorous and germanium, x ranges from about .05 to .25, y ranges from about 0 to .75, and b ranges from about 14 to 28 atom percent, having a value of magnetostriction of about -6 x 10-6 to 4 x 10-6 and a saturation of about 0.2 to 1.0T.

2. A magnetic alloy, as recited in claim 1, wherein x ranges from about .05 to .15, y ranges from about 0 to .25 and b ranges from about 17 to 22 atom percent said alloy having a value of magnetostriction of about -3 x 10-6 to +1 x 10-6 and a saturation induction of about 0.3 to 0.6T.