Magnetic properties of TmxDy1−xFeO3 single crystals

Solid State Communications, Vol. 16, pp. 393—395, 1975.

Pergainon Press.

Printed in Great Britain

MAGNETIC PROPERTIES OF Tm~Dy1...~FeO3 SINGLE CRYSTALS V.N. Derkachenco and V.A. Khokhlov Physico—Technical Institute, Academy of Science of the Ukrainian SSR, 340048, Donetsk, U.S.S.R. and A.M. Kadomtseva and M.M. Lukina M.V. Lomonosov State University, Moscow, U.S.S.R. (Received 31 October 1974 by E.A. Kaner)

The magnetic behaviour of Tm~Dy1.~FeO3 (x = 0.3; 0.5; 0.7; 1.0) single crystals in the temperature range 90—4.2°K were investigated. The transition from the weak ferromagnetic to antiferromagnetic state was observed at about 90 K for Tm0 3Dy0 7FeO3 single crystal. The reorientation of weak ferromagnetic moment from c- to a-axis was observed for Tm0~7Dy0~3FeO3 single crystal at 35_650 K. The magnetic structure change of iron and rareearth ions took place when external magnetic field was applied. The thulium and disprosium ion interaction does not essentially influence on the single crystal magnetic properties of the substituted compounds in a low temperature range.

THE DISPROSIUM and thulium orthofemtes are known to show magnetic structure changes at low temperatures. The transition from weak ferromagnetic to antiferromagnetic state (the magnetic structure transition from G~F~ to G~)is observed in the disprosium orthoferrite at about 36°K.’ In thulium orthoferrite the weak ferromagnetic moment turns 2’3 from c- to a-axis (GXFZ—GZFX) at 80—92° K. At lowthetemperatures the different types of antiferro

The measurements had shown that the rare-earth ions have a rather high anisotropy which remains even in fields up to 50 kOe in a low temperature region. At liquid helium temperature the behaviour of the curves (Fig. 1) indicates the rare.earth antiferromagnetic ordering. The component of the magnetic moment along the c-axis concentration in theincreases Tm~Dywith increasing thulium 512B value up to at 50 kOe field in TmFeO 1_~FeO3 3. Decrease of the magnetic moment components along a- and b-axis having maximum value in DyFeO 6 The disprosium orthoferrite is 3 was alsotoobserved. known have a metamagnetic transition from the A~G~ to F~C~ structureunder the influence of magnetic field applied along the a-axis and to the F~C~ structure if the field is parallel to the b-axis.4 It is

magnetic rare-earth ion orderings are observed in these 4 orthoferrites. Synthesis and investigation of singlesocrystals the mixed compounds were of interest, far as itof was expected in the appearance of new properties due to the change of interaction for different ions. The samples of Tm~Dy 1_~ FeC)3 (x = 0.3; 0.5; 0.7; 1.0) single crystals were prepared by the flux 5 method similar to that proposed by Remeika.

reasonable to suppose that the magnetic structure change of disprosium ion is done by the samechange way in the substituted compounds. The monotomc of the magnetic moment of the investigated crystals, in which disprosium ions are substituted by thulium 393

394

MAGNETIC PROPERTIES OF Tm~Dy1...~FeO3 TmFeO3

Tm07D~3FeO3

90

90

/

60

:1,,

60

-

x_x.

/

,~ ‘2

\~

5\

>~

\

j..•• • ..—..——-•-.•

I

0 ..~ ____________________ I 50 tOG

~‘~~~à.*.akA

Xb

~

__________________________________________________ ____________________

0

%

T°K

~

50

100

T1(

~

10

_______________________

20

30

H,

Koe

40

50

0

Tm0 5D~5FeO3 90

5

A Tm~Dy07FeO3 ‘A

Tm03Dy07FeO3

C~OO

X

/

-

-

xxC 30

0

Vol. 16, No.4

I 20 30 H, Koe

Tm03Dy07FeQ3 90

-

40

Tm05Dy05FeO3

‘2

~

X~

5-

•__•_••__•___-.•8

•,

.-..—.-

Tm05Dy,~5FeO3 A

ElcI. .

~

/

-

-

50

‘C C

/“

-

/~•

60

£

-

1’/

50

30

‘

00

T°K

Tm0 7Dy03FeO3

~‘

0I

I 20

30

I 40

I~,tC’~ItO 50

I 20

H,

Koe

Tm0 7Dy0feO3

•~\.

if

H,

I 30

I 40

2

A

~

I 50

XC

Koe

0

FIG. 1. The magnetization curves of Tm~Dy1_~FeO3 (x = 1.0; O.7~0.5; 0.3) single crystals along a _(A), b (S), c (x) axes at 4.2°K.

‘-i....L.3x9 50

T~X

I

00

_________________________

50

tOO

T~X

—

ions, suggests a very weak interaction between them and it does not influence so much on their magnetic properties. Magnetization a = -~~/o~ + cr~+ a~dependence of Tm~Dy1..~FeO3 single crystals on Tm concentration in 40 kOe at 4.2°K is given in Table 1. Data for DyFeO3 are taken from reference 6.

X

0

‘../o~+ a~+3 o~ 180.5 (e.m.u./g) cm

FIG. 2. Temperature dependences of spontaneous magnetizations and susceptibilities for Tm~Dyi_~ FeO3 (x = 1.0; 0.7; 0.5; 0.3) single crystals. decrease from 8°K. It may probably become zero at a lower temperature as for x = 0.3. Thus, one can see that the substitution of disprosium by thulium leads to a lower transition temperature from the weak ferromagnetic to antiferromagnetic state (the Morin temperature) in comparision with the unsubstituted disprosium orthoferrite.

Table 1

=

50

T°K tO

0

a

________________

100

£

~

~,I

—

I

/

60 30

0

0.3

0.5

0.7

1.0

126

107

94

93.5

The temperature dependences of spontaneous magnetizations for all the substituted compounds have character indicating the transitions connected with the spin reorientation (Fig. 2). It was observed that the weak ferromagnetic moment disappears and the crystal becomes antiferromagnetic (transition G~F2—G~)for x = 0.3 at 9°K. For a single crystal ofx = 0.5 the magnetization along c-axis begins to

The external magnetic along c-axis reduces the Morin temperature. Thefield threshold field inducing the weak ferromagnetic transition was about 12 kOe for Tm 0~3Dy07FeO3at 4.2°K. The field of about 3 kOe applied to the a-axis has induced the transition from the G~F~ to G~F~ structure at temperatures lower than 30°Kfor x = 0.3 and 0.5. The magnetic anisotropy constant in the (ac)-plane in substituted compounds decreases in comparison with the disprosium orthoferrite, especially for Tm0~7Dy0,3FeO3, where the spin reorientation in the (ac)-plane (GXFZ —G~F~ transition) takes place in the temperature

Vol. 16, No.4

MAGNETIC PROPERTIES OF Tm~Dy1.~FeO3

range 35—65°K (Fig. 2). One can observe the similar transition for the unsubstituted thulium orthoferrite in the temperature range 85—100°K. The reorientation region TmFeO3 differs evidently frominthe 2’3indue to the presence of Fe4~ions thereported samples one leads to an increase of reorientation temperature.7 that The interactions of the rare-earth and iron in Tm 0~7Dy0~3FeO3 along a-axis were positive as opposed to TmFeO3. This leads to a considerable increase of the magnetic moment in a low temperature region.

395

Thus, the substitution of disprosium ions by thulium ones in DyFeO3 leads to a decrease of magnetic anisotropy constant and that is why the different types observed. of the spin reorientation of the iron sublattice were Acknowledgement

—

The authors wish to express their

sincere appreciation to N.M. Kovtun for his comments on the paper s results and for many stimulating discussions.

REFERENCES 1. 2.

WHITE R.L.,J.AppL Phys~40, 1061 (1969). DURODA C., MIYADAI T., NAEMURA A., NEIZEKI N. and TAKATA H., Phys. Rev. 122, 446 (1961).

3.

BELOV K.P., KADOMTSEVA A.M., MEDVEDEV S.A., USKOV V.V. and CHERVONENKIS A.Ja., J. Exp. Theor. Phys. 57, 1157 (1969).

4.

APOSTOLOV A. and SIVARDIERE J., CR. Acad. Sci. 267, 25, B1315 (1968).

5.

REMEIKA J.P.,J. Am. Chem. Soc. 78,4259(1956).

6. 7.

GORODETSKY G., SHARON B. and STRIKMAN S.,J. Appi. Phys. 39, 1371 (1968). GYORGY E.M., REMEIKA J.P. and WOOD D.L., J. Appi. Phys. 39, 3499 (1968).