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Submitted on 1 Jan 1971
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FINE PARTICLES’ AND FAST RELAXERS’
INFLUENCE ON THE MAGNETIC RF THRESHOLD FIELDS AND LOSSES IN YIG
C. Borghese, R. Roveda
To cite this version:
C. Borghese, R. Roveda. FINE PARTICLES’ AND FAST RELAXERS’ INFLUENCE ON THE MAGNETIC RF THRESHOLD FIELDS AND LOSSES IN YIG. Journal de Physique Colloques, 1971, 32 (C1), pp.C1-150-C1-152. �10.1051/jphyscol:1971149�. �jpa-00214476�
JOURNAL DE PHYSIQUE Colloque C I, supplkment au no 2-3, Tome 32, Fbvrier-Mars 1971, page C 1
-
150FINE PARTZCLES'
ANDFAST RELAXERS' INBLUEWE
ON THE MAGNETIC RF THRESHOLD FIELDS AND LOSSES IN MG
C. BORGHESE and R. ROVEDA
Research Department, Selenia S. p. A., Roma 00131, Italy
R6sum6.
-
On donne les gsultats de l'ktude des series d'kchantillons de YIG : 1. dopes avec terres raresa
grains gros ; 2. a grains fins et 3. dopes avec terres rares, a grains -Ens. augmente tr&s rapidement avec A H e f r a champ faible pour les materiaux YIG B grains fins, tandis que IAHk se comporte linkairementavecpente = 4 pour les materiaux dopes avec terres rares, a grains gros. ( , h c r i t obeit B une loi du type i j - 1 pour YIG, approximativement du type i j - Q . 4pour 0.03 Sm3+-YIG. On a aussi essay6 d'en donner une simple explication. F*, le facteur de mMte a haute puissance crste, croPt de 2,7 a 12,s lorsque Z decroit de 14 a 1 micron pour YIG.
Abstract. - Three series of samples are examined : 1. coarse grained, rare earth-doped YIG ; 2. fine pained YIG and 3. fine grained, rare earth-doped YIG. .AHx increases very rapidly with low-field AHaf in the fine gra~ned YIG, as compared with the linear, 112-slope in coarse grained, rare earth-doped YIG. I l h c r i t behaves as 2-1 in YIG, as 5 9 . 4 in 0.03 Sm3+-doped YIG. A simple tentative explanation is given. The high power figure of merit, F*, raises from 2.7 to 12.5 on passing from a 14-micron to a 1-micron YIG sample.
The experimental work presented here was under- taken to study the high power and loss microwave properties of YIG compositions : 1. fine grained by hot pressing and subsequent annealing to obtain scaled average grain size (Z) values ; 2. doped with rare earth (R. E.) relaxers, and ; 3. R. E. - doped and fine grained. In the line of previous work (Pala- d i n ~ et al. [I], Vrehen et al. [2], Borghese et al. [3], Roveda et al. [4], Patton [5]) the investigated mate- rials seemed promising for achieving new information on the above properties. The following quantities were measured : saturation magnetization, 4 nM ; resonance linewidth, A H ; the imaginary part of the permeability at static external field Ho = 0 and Ho = 4 nM/3, respectively p: and
&,
; the threshold fields for parallel pump and perpendicular pump instabilities, at their minimum, Ilhc,it and ,ticri,. From pzat, ,,hCri, and ,hCri, also the effective linewidth at the saturation point (SchIomann [6] ; Patton [7]) AH,,, and the spin wave linewidths II.AHK and ,AHK were respectively calculated. The h ~ g h power figure of merit on spheres P* was calculated following Schlo- mann and coworkers [8]. All microwave measurements were performed at room temperature and X band.Dielectric losses, tan 6, resulted for all samples
< 5 x
Most of the R. E.-doped YIG's were prepared by
conventional ceramic technique and their composi- tion and properties are listed in Table I. The fine grained (fg) compositions were hot pressed at 1 100 O C for 15' under a lo3 kg cm-2 pressure and annealed for two hours at different temperatures. Preparation features and properties are listed in Table 11. The butterfly curves of the fg YIG samples are similar to those obtained by Patton [5] in his HP series. A regressive shift of
-
200 Oe of the static field for the minimum is observed on going towards small SE.The results of figure 1 show that for R. E.-doped, coarse grained (cg) YIG's, ,AH, is linear in AH,, at the saturation point and has the predicted slope of one-half : .AHk is related to the relaxation fre- quency wk = 012 ( o is the uniform mode frequency at which AH,, and AH were measured). The same loss mechanism generates AH, and AH,,. A H is linear with slope one in AH,,, therefore porosity and anisotropy do not change much from one sample to another. As reported in Table I, R. E.-doped cg YIG's have almost constant F*, independently of dopant's nature and concentration and close to the theoretical limit (Schlomann et al. [6])
F* E (0/0& (1 - oM/6 O ) W 1.7 .
In figure 1 at the top right, .h,,,, vs R.E.-concentration is plotted. The behavior is linear and the slope depends on the dopant's nature.
Sample No.
and composition - 1. Y3Fe5OI2
2. Y2.994H00.006Fe5012 3. Y2.97H00.03Fe5012 4. Y2.989D~0.011Fe5O12 5. Y2.97D~o.o3Fe5O12 6. Y2.97Sm0.03Fe5012 7' Y2.97Yb0.03Fe5012 8- Y2.91Yb0.09Fe5012
9- Y2.88Yb~.12Fe5012
10. Y2.9ssHoo.01sFe5012
TABLE I
Properties of R. E.-doped YIG, conventionally$red
4 ZM AH CLS = d a t
(GI ( 0 4 ( X lo3)
- -
1 770 23 0.43
1 795 28 1.20
1 780 66 4.00
1 790 35 1.40
1 760 50 2.80
1 770 35 1.90
1 795 24 0.65
1 770 28 0.94
1 760 32 1.10
1 800 48 3.00
Article published online by EDP Sciences and available at http://dx.doi.org/10.1051/jphyscol:1971149
FINE PARTICLES' AND FAST RELAXERS' INFLUENCE
Some properties o f j n e grained YIG and R. E.-doped YIG compositions.
All samples were hot pressed at 1 100 O C for 15'. A : O C of annealing temperature for 2 hours
Sample No., -
composition x
and A ( O C )
-
(PI
-1. YIG, A : 1200 1.2
2. YJG, A : 1 300 0.9 3. YIG, A : 1 400 1.5 4. YIG, A : 1420 5.0 5. YIG, A : 1 460 14.4 6. Y2.9ssHoo.olsFe5Olz 1.1 7. Y2.97Sm0.03Fe5012 1.2
A H
(Oe) ,ug x lo3 - -
8 1 0.88
37 0.82
45 0.51
25 0.30
20 0.16
64 0.82
78 2.6
,AHk and AH vs AH,, have been plotted in figure 1 also for the fg YIG samples. It is seen that the relaxa- tion mechanism is quite different from the previous one, and its nature is not explained, In figure 2 I,hcri,
FIG. 1. - Perpendicular pump spin-wave linewidth LAHk, as a function of the off-resonance effective linewidth AHdn at X band for : ( 0 ) fast relaxer-doped (fr) YZG and (e) fine grained (fg) YIG. Resonance linewidth AH against AH,ff is also shown for the fr
(n),
and fg (.) samples. At the top right Lhcrit vsR. E, concentration in the fr series is shown.
has been plotted as a function of Z in a log-log scale.
Several observations can be made. Ilhcrit cc 2-' for fg YIG's, in agreement with Patton, while
h cc 2 - 0 . 4 crit
for the straight line connecting the two points related to the Y
,.,,
Smo.o,Fe,O,, composition. In the same figure, previous results on fine grained Ni-ferrites [3]and on Mg, Mn(Co)-ferrites [4] have been plotted.
It is immediately recognized that relaxing ions act to decrease the slope of pure compositions, the more so, the higher the concentration. A tentative approximate explanation can be proposed as follows : by main- taining the assumption of the transit-time-limited spin-wave life time (Vrehen [2]) and the ?-independence
FIG. 2. - Average grain size-dependance of the parallel pump threshold field at 9.2 GHz in fine grained YIG samples and in a 0.03 Sm3+-YIG composition. The behavior of Ni-ferrite and Mg, Mn(Co)-ferrite is shown for comparison.
of the spin-wave group velocity v, [5] it is suggested that another contribution adds to IIAHk = Ilhcrit wIuM.
This can be ascribed to an intrinsic relaxation time )>
zkSin, = l/y related to the reduction of the mean free path by direct and rapid relaxation to the lattice of the k-mode magnon travelling through the grain of size 2. Thus, in presence of a relaxing impu- rity :
Ilhcrit = (w
I
V g I)l(y2 4 n M 2 ) llhcrit,int (1) Reasonably assuming that Ilhc,i,,int sz 0 for pure YIG, deriving oI
v I/yw, = 2.12 x lod3 Oe cm, if/ v,
1
z 2 x lo4, crn.
s-I, from the MG curve in figure 2, Ilh,,it can be evaluated for a fg R. E.-doped YIG composition, provided Ilh,rit,int is known for a cg sample of the same composition. This is done here on conventionally fired Y2~985Hoo.o15Fe50,, and Y2~,,Smo~03Fe50,2 (samples NO 10 and NO 5 of Table I) which yield Ilhc,it,int = 17.8 and 15.0 Oe, respectively. Application of eq. 1 to the related fg compositions (NO 6 and NO 7 of Table II) provide ,,hcrit = 35.3 and 34.1 Oe against 35.0 and 37.2 Oe asC 1 - 152 C . BORGHESE AND R. ROVEDA
found experimentally. It is interesting to note that all increase of P* for the fg YIG materials, while an the Ilh,,it(;F) - curves reach a value of the same order approximately twofold increase occurs for the fg of magnitude (from 60 Oe to 100 Oe) if extrapolated R. E.-doped YIG materials. Another unpredicted in the submicron region, between 0.2 y and 0.5 p. feature occurs : although
odm
z 0.5, well below In that region, small grain sizes seem to dominate the limit for domain resonance losses, > ,,:y for the relaxation process, independently of composition. the fg YIG No simple explanation is given Inspection of Tables I and I1 show a more than fourfold at this time on the cause of this phenomenon.References
[I] PALADINO (A. E.), WAUGH (J. S.), GREEN (J. J.) and [4] ROVEDA (R.) and BORGHESE (C.), J. Appl. Phys., 1970, BOOTH (A. E.), J. Appl. Phys., 1966, 37, 3371. 41, 2729.
[2] VREHEN (Q. H. F.), BELJERS (H. G.) and DE LAU [5] PATTON (C. E.), J. Appl. Phys., 1970, 41, 1637.
(J. G. M.), IEEE Trans. Magnetics, 1969, Mag-5, [6] SCHLOMANN (E.), J. Phys. Chem. Solids, 1958, 6, 242.
617. [7] PATTON (C. E.), Phys. Rev., 1969, 179, 352.
[3] BORGHESE (C.) and ROVEDA (R.), J. Appl. Phys., 1969, [8] SCHLOMANN (E.), GREEN (J. J.) and SAUNDERS (J. H.),
40, 4791. IEEE Trans. Magnetics, 1965, Mag-1, 168.
