Antiferromagnetic-Resonance Measurements in Europium Telluride

Battles, J. W.; Everett, Glen E.

doi:10.1103/physrevb.1.3021

Cited by 69 publications

(30 citation statements)

References 26 publications

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“…This accord between both interactions seems to be the reason that in EuTe the AF-SF phase line is depressed to B o = 0 and that the system stays always in the SF phase once a magnetic field has been applied. This view-point is at variance with earlier suggestions of a spin-fiop transition occuring in EuTe [1,15], but it conforms to computer simulations [11] which proved that the dipole-dipole anisotropy is not strong enough to result in an AF-SF transition at finite fields. In fact, the differentiated magnetization curves (Fig.…”

Section: T~v(x)/tn(1) Was Increasedsupporting

confidence: 85%

Biquadratic exchange and critical behaviour in the diluted antiferromagnet EuxSr1−xTe

Köbler

Apfelstedt

Fischer

et al. 1993

Z. Physik B - Condensed Matter

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Abstract. Magnetization, specific heat, magnetocaloric effect, and neutron diffraction measurements have been performed in order to better understand the magnetic interactions and phase transitions in the diluted antiferromagnetic system EuxSrl_xTe. Due to the low N6el temperature of TN=9.8 K and the associated small critical field of Be(T= 0)= 7.5 T, EuTe provides the opportunity to change the angle between the antiferromagnetic moments continuously between 180 ~ and 0 ~ by applying a magnetic field and allows thus to probe the type of the magnetic interaction. It is found that in addition to the common bilinear Heisenberg exchange mechanism there is evidence for a small biquadratic exchange term, which has important consequences on the critical behaviour of EuxSr~_xTe. In the case of EuTe the biquadratic exchange supports the antiferromagnetic order, such that virtually no anisotropy exists and this restricts the antiferromagnetic (AF) to spin-flop (SF) transition to B0 = 0. On dilution with strontium, the biquadratic interaction decreases strongly and changes its sign at x~0.83 thus favouring the perpendicular moment orientation. This acts like an anisotropy on the dominating antiferromagnetic bilinear interaction and shifts the AF-SF phase line to finite fields which reach values of 0.3 T for T~ 0. No bicritieal behaviour is observed, but instead, the SF phase is the state of lowest energy in a small temperature interval below TN. The critical exponent ~(x) of the specific heat decreases in a non-linear way with dilution starting from a large positive value for EuTe. e(x) is close to the Heisenberg value -0.12 near x~0.83 where the biquadratic interaction is zero. The same applies for the exponent fl of the sublattice magnetization.

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Section: T~v(x)/tn(1) Was Increasedsupporting

confidence: 85%

Biquadratic exchange and critical behaviour in the diluted antiferromagnet EuxSr1−xTe

Köbler

Apfelstedt

Fischer

et al. 1993

Z. Physik B - Condensed Matter

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“…Additional in-plane anisotropy favors spin alignment in any of the three equivalent ͗11− 2͘ azimuths, forming the S domains. 7 Below T N , the AFM ordering of EuTe provides a straightforward separation between charge and magnetic diffraction peaks. In a very recent work, we used resonant x-ray diffraction to study the magnetic order in EuTe/PbTe multilayers.…”

Section: Introductionmentioning

confidence: 99%

Magnetic resonant x-ray diffraction study of europium telluride

et al. 2008

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Here we use magnetic resonant x-ray diffraction to study the magnetic order in a 1.5 m EuTe film grown on ͑111͒ BaF 2 by molecular-beam epitaxy. At Eu L II and L III absorption edges, a resonant enhancement of more than two orders was observed for the → Ј diffracted intensity at half-order reciprocal-lattice points, consistent with the magnetic character of the scattering. We studied the evolution of the ͑ 2 ͒ magnetic reflection with temperature. When heating toward the Neel temperature ͑T N ͒, the integrated intensity decreased monotonously and showed no hysteresis upon cooling again, indicating a second-order phase transition. A power-law fit to the magnetization versus temperature curve yielded T N = 9.99͑1͒ K and a critical exponent ␤ = 0.36͑1͒, which agrees with the renormalization theory results for three-dimensional Heisenberg magnets. The fits to the sublattice magnetization dependence with temperature, disregarding and considering fourth-order exchange interactions, evidenced the importance of the latter for a correct description of magnetism in EuTe. A value of 0.009 was found for the ͑2j 1 + j 2 ͒ / J 2 ratio between the Heisenberg J 2 and fourth-order j 1,2 exchange constants. The magnetization curve exhibited a round-shaped region just near T N accompanied by an increase in the magnetic peak width, which was attributed to critical scattering above T N . The comparison of the intensity ratio between the ͑

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“…Increasing field aligns the spins more and more and at the critical field B c = 7.4 T at T= 0 a second order phase transition to the paramagnetic state occurs. As a result of an additional in-plane anisotropy, the [ll2]-directions are the easy directions [9,10]. The magnetic phase diagram of EuTe has been investigated theoretically by mean-field and Monte Carlo calculations [111.…”

Section: Introductionmentioning

confidence: 99%

Specific heat of Eu x Sr1−x Te

Scheer

Wosnitza

Löhneysen

1991

Z. Physik B - Condensed Matter

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In this paper, we report on measurements of the specific heat C of single-crystalline EuxSrl_xTe at temperatures between 60 mK and 15 K and in magnetic fields up to 6 T. Pure antiferromagnetic EuTe shows unusual critical behavior in the vicinity of the N6el temperature T N = 9.8 K with a positive critical exponent instead of the 3d-Heisenberg exponent c~---0.12. Possible reasons for this discrepancy between theory and experiment include magnetic anisotropy effects due to magnetic dipole-dipole interactions, which may give rise to a cross-over of the critical behavior very close to T N. This anisotropy is also seen in the specific heat below 1 K where an exponential decay of C is observed, and in the dependence of the magnetic susceptibility on the direction of the applied field. With increasing dilution of EuTe with nonmagnetic Sr, the critical behavior changes: ~ becomes negative and decreases continuously towards ~ ~-1 at x~x c. This concentration dependence of e was previously observed in the diluted ferromagnetic system EuxSr ~ _xS. Our data thus support that the apparent change in the critical behavior depends on the degree of disorder. Samples with concentration x lower than the critical concentration x c reveal spin-glass behavior in the specific heat. In addition, the dependence of T N on magnetic fields is discussed. The data yield a normalized magnetic phase boundary Bc(T)/Bc(T=O ) vs. TN(B)/TN(B=O ) which is independent of concentration.

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Antiferromagnetic-Resonance Measurements in Europium Telluride

Cited by 69 publications

References 26 publications

Biquadratic exchange and critical behaviour in the diluted antiferromagnet EuxSr1−xTe

Biquadratic exchange and critical behaviour in the diluted antiferromagnet EuxSr1−xTe

Magnetic resonant x-ray diffraction study of europium telluride

Specific heat of Eu x Sr1−x Te

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