Muon-spin-relaxation study of the critical longitudinal spin dynamics in a dipolar Heisenberg ferromagnet

Yaouanc, A.; Réotier, P. Dalmas de; Gubbens, P.C.M.; Mulders, A. M.; Kayzel, F.E.; Franse, J.J.M.

doi:10.1103/physrevb.53.350

Cited by 22 publications

(32 citation statements)

References 22 publications

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“…One of the systems that has been extensively studied is the intermetallic ferromagnets. For example, GdNi 5 is an axial ferromagnet with a critical temperature of approximately T c ∼31 K [96]. It is characterised by extremely weak magnetic anisotropy arising from the dipole moment interaction between the Gd 3+ .…”

Section: Critical Point Spin Dynamicsmentioning

confidence: 99%

“…It is characterised by extremely weak magnetic anisotropy arising from the dipole moment interaction between the Gd 3+ . ZF muon measurements were performed as a function of temperature on two crystalline samples with different orientations with respect to the muon's initial spin direction (c-axis either parallel or perpendicular to the muon's spin) [96]. It was shown that above T c , the relaxation rate is temperature independent, reflecting the vanishing pair correlations at high temperature, as a result of the relatively low density of states at the Fermi level [97].…”

Section: Critical Point Spin Dynamicsmentioning

confidence: 99%

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Muon spin spectroscopy: magnetism, soft matter and the bridge between the two

Nuccio

Schulz

Drew

2014

J. Phys. D: Appl. Phys.

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The use of implanted muons to probe the spin dynamics and electronic excitations in a variety of magnetic and non-magnetic materials is reviewed and is split into three main sections, the first of which is an introduction to the historical context and background of the muon technique, which includes a basic introduction to the experimental method and underlying theoretical models. The second section is concerned with inorganic magnetic systems, starting with an overview of spin dynamics around critical points in ordered magnets. This is followed by an introduction to the early work on spin glasses, liquids and ices, which then continues onto the recent research in this area, including a discussion of some of the more controversial recent work on spin ices and magnetic monopoles. Information obtained by muons vital to two very important technological areas -magnetic semiconductors and next-generation energy materials -closes the discussion of inorganic magnetic materials. The final section is concerned with spin dynamics and magnetism in soft materials, and starts with discussing many of the key results in molecular magnets and organic spintronics. Spin dynamics in organic semiconductors, polymers and biological molecules is then covered, where contradictory experimental and theoretical work on charge carrier motion is presented. The similarities between the low-field relaxation rates in these "conducting" organic materials is compared to measurements of the electron spin relaxation measured in localised electronic states, obtained from high-field avoided level crossing spectroscopy in similar (and the same) materials.

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Section: Critical Point Spin Dynamicsmentioning

confidence: 99%

Section: Critical Point Spin Dynamicsmentioning

confidence: 99%

Muon spin spectroscopy: magnetism, soft matter and the bridge between the two

Nuccio

Schulz

Drew

2014

J. Phys. D: Appl. Phys.

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“…3. We note two features: (i) λ d = 0.029(3) µs −1 is constant below ∼100 K, and (ii) with decreasing temperature there is an unusual step-like increase in λ d below T M but no sign of the paramagnetic-state divergence that is often found in frustrated and unfrustrated magnets [17][18][19][20] due to critical slowing down of dynamic fluctuations. This absence suggests a mean-field-like transition.…”

mentioning

confidence: 99%

Magnetic transition, long-range order, and moment fluctuations in the pyrochlore iridate Eu2Ir2O
Zhao
¹
,
Mackie
²
,
MacLaughlin
³

et al. 2011
Phys. Rev. B
89
24
96
1
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Muon spin rotation and relaxation experiments in the pyrochlore iridate Eu 2 Ir 2 O 7 yield a welldefined muon spin precession frequency below the metal-insulator/antiferromagnetic transition temperature T M = 120 K, indicative of long-range commensurate magnetic order and thus ruling out quantum spin liquid and spin-glass-like ground states. The dynamic muon spin relaxation rate is temperature-independent between 2 K and ∼T M and yields an anomalously long Ir 4+ spin correlation time, suggesting a singular density of low-lying spin excitations. Similar behavior is found in other pyrochlores and geometrically frustrated systems, but also in the unfrustrated iridate BaIrO 3 . Eu 2 Ir 2 O 7 may be only weakly frustrated; if so, the singularity might be associated with the small-gap insulating state rather than frustration.

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“…The two scaling variables at play depend on two material parameters: ξ 0 , the magnetic correlation length at T = 2T C , and q D , the dipolar wave vector which is a measure of the strength of the exchange interaction relative to the dipolar energy. This model initially derived for the paramagnetic phase applies also below T C [16]. Specifically, the model predicts that…”

mentioning

confidence: 99%

“…λ Z (T ) has been computed several years ago [15] for the critical regime of dipolar Heisenberg ferromagnets and has been successfully compared to experiments [15][16][17]. It is based on the derivation of the static and dynamical scaling laws from mode coupling theory [18].…”

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confidence: 99%

Evidence for Weak Itinerant Long-Range Magnetic Correlations inUGe2

et al. 2002

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Positive muon spin relaxation measurements performed on the ferromagnet UGe2 reveal, in addition to the well known localized 5f -electron density responsible for the bulk magnetic properties, the existence of itinerant quasi-static magnetic correlations. Their critical dynamics is well described by the conventional dipolar Heisenberg model. These correlations involve small magnetic moments.PACS numbers : 74.70. Tx, 76.75.+i The discovery of superconductivity below 1 K within a limited pressure range in the ferromagnet UGe 2 [1-4] provides an unanticipated example of coexistence of superconductivity and strong ferromagnetism. The electronic pairing mechanism needed for superconductivity is believed to be magnetic in origin. However, it is amazing that ferromagnetically ordered uranium magnetic moments with so large magnitude (∼ 1.4 µ B at ambient pressure as deduced from magnetization measurements) are directly involved [5]. Since the pairing must involve the conduction electrons, it is important to characterize their magnetic properties. Because of the restrictions imposed by the magnetic form factor, this can not be done by diffraction techniques. As the muons localize in interstitial sites, they have the potentiality to yield information on the conduction electrons. Here we show, using the muon spin relaxation technique, that UGe 2 is actually a dual system where two sub-states of f electrons coexist. We indeed report the existence at ambient pressure of itinerant long-range magnetic correlations with magnetic moments of ∼ 0.02 µ B and a spectral weight in the megahertz range. A quantitative understanding of this state is moreover reached assuming that these correlations involve only long wavelength fluctuation modes.UGe 2 is a ferromagnet with a Curie temperature T C ≃ 52 K which crystallizes in the orthorhombic ZrGa 2 crystal structure (space group Cmmm) [6,7]. Magnetic measurements indicate a strong magnetocrystalline anisotropy [8,9,3] with easy magnetization axis along the a axis.We present results obtained by the muon spin relaxation (µSR) technique. Fully polarized muons are implanted into the studied sample. Their spin (1/2) evolves in the local magnetic field, B loc , until they decay into positrons. Since the positron is emitted preferentially in the direction of the muon spin at the decay time, it is possible to follow the evolution of the muon spin polarization [10,11]. The measured physical parameter is the so-called asymmetry which characterizes the anisotropy of the positron emission. Below T C , if B loc has a component perpendicular to the initial muon beam polarization, S µ (taken parallel to Z), we expect the asymmetry to display spontaneous oscillations with an amplitude maximum for B loc ⊥ S µ . On the other hand, if B loc S µ , the asymmetry can be written as the product of an initial asymmetry related to sample, a s , and the muon spin relaxation function, P Z (t), which monitors the dynamics of B loc .UGe 2 crystals were grown from a polycrystalline ingot using a Czochralski tri-arc ...

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Muon-spin-relaxation study of the critical longitudinal spin dynamics in a dipolar Heisenberg ferromagnet

Abstract: Muon-spin-relaxation study of the critical longitudinal spin dynamics in a dipolar Heisenberg ferromagnet Yaouanc, A.; de Reotier, P.D.; Gubbens, P.C.M.; Mulders, A.M.; Kayzel, F.E.; Franse, J.J.M.

Cited by 22 publications

References 22 publications

Muon spin spectroscopy: magnetism, soft matter and the bridge between the two

Muon spin spectroscopy: magnetism, soft matter and the bridge between the two

Magnetic transition, long-range order, and moment fluctuations in the pyrochlore iridate Eu2Ir2O
Zhao
¹
,
Mackie
²
,
MacLaughlin
³

et al. 2011
Phys. Rev. B
89
24
96
1
View full text Add to dashboard Cite

Evidence for Weak Itinerant Long-Range Magnetic Correlations inUGe2

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Muon-spin-relaxation study of the critical longitudinal spin dynamics in a dipolar Heisenberg ferromagnet

Abstract: Muon-spin-relaxation study of the critical longitudinal spin dynamics in a dipolar Heisenberg ferromagnet Yaouanc, A.; de Reotier, P.D.; Gubbens, P.C.M.; Mulders, A.M.; Kayzel, F.E.; Franse, J.J.M.

Cited by 22 publications

References 22 publications

Muon spin spectroscopy: magnetism, soft matter and the bridge between the two

Muon spin spectroscopy: magnetism, soft matter and the bridge between the two

Magnetic transition, long-range order, and moment fluctuations in the pyrochlore iridate Eu2Ir2OZhao1, Mackie2, MacLaughlin3 et al. 2011Phys. Rev. B8924961View full textAdd to dashboardCite

Evidence for Weak Itinerant Long-Range Magnetic Correlations inUGe2

Contact Info

Product

Resources

About

Magnetic transition, long-range order, and moment fluctuations in the pyrochlore iridate Eu2Ir2O
Zhao
¹
,
Mackie
²
,
MacLaughlin
³

et al. 2011
Phys. Rev. B
89
24
96
1
View full text Add to dashboard Cite