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Baek, S.‐H.; Klingeler, R.; Neef, Christoph; Koo, Changhyun; Büchner, B.; Grafe, H.-J.

doi:10.1103/physrevb.89.134424

Cited by 10 publications

(6 citation statements)

References 35 publications

(46 reference statements)

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“…Furthermore, similar effective magnetic moments of m eff ¼ (5.20 AE 0.02) m B for Li 0.5Àd CoPO 4 and (5.08 AE 0.02) m B for Li 1Àg CoPO 4 were found. Both values exceed the spin-only value of high-spin Co 2+ and Co 3+ (3.9 m B and 4.8 m B , respectively), demonstrating a non-negligible orbital contribution 42. Taking into account the nite angular momentum, effective magnetic moments of 5.2 m B and 5.5 m B for high-spin Co2+ and Co 3+ in the O h symmetry ( 5 t 2g and 4 t 1g ground state) are expected in the weak spin-orbit coupling limit.…”

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confidence: 75%

Direct synthesis and characterization of mixed-valent Li_0.5−δCoPO₄, a Li-deficient derivative of the Cmcm polymorph of LiCoPO₄

et al. 2017

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confidence: 75%

Direct synthesis and characterization of mixed-valent Li_0.5−δCoPO₄, a Li-deficient derivative of the Cmcm polymorph of LiCoPO₄

et al. 2017

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“…The magnitude of the effective magnetic moment (m eff ) has been debated in the literature for pure olivines. 30,32,[37][38][39][59][60][61] It has been found experimentally that the observed magnitude of m eff can exceed the spin-values of 3.87 m B and 4.89 m B for both the pure olivines, LCP and LFP, respectively. Indeed, these spin-only values are expected only for octahedrally coordinated, HS Co-3d 7 and Fe-3d 6 configurations with full quenching of the orbital moments.…”

Section: Experimental Magnetic Propertiesmentioning

confidence: 92%

“…For instance, the value of g for a single crystal (SC) of LCP is 2.17, 30 while for the polycrystalline (PC) sample, the reported value by Baek et al is 2.27. 60 Fig. 5 Computed spin and orbital magnetic moment direction for each magnetic ion (Co -blue sphere; Fe -brown sphere) for (b) x = 0.00, (c) x = 0.25, (d) x = 0.50, (e) x = 0.75, and (f) x = 1.00.…”

Section: Computed Magnetic Structure and Magnetic Propertiesmentioning

confidence: 99%

Magnetism in olivine-type LiCo_1−xFe_xPO₄cathode materials: bridging theory and experiment

Singh

Gershinsky

Kosa

et al. 2015

Phys. Chem. Chem. Phys.

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In the current paper, we present a non-aqueous sol-gel synthesis of olivine type LiCo1-xFexPO4 compounds (x = 0.00, 0.25, 0.50, 0.75, 1.00). The magnetic properties of the olivines are measured experimentally and calculated using first-principles theory. Specifically, the electronic and magnetic properties are studied in detail with standard density functional theory (DFT), as well as by including spin-orbit coupling (SOC), which couples the spin to the crystal structure. We find that the Co(2+) ions exhibit strong orbital moment in the pure LiCoPO4 system, which is partially quenched upon substitution of Co(2+) by Fe(2+). Interestingly, we also observe a non-negligible orbital moment on the Fe(2+) ion. We underscore that the inclusion of SOC in the calculations is essential to obtain qualitative agreement with the observed effective magnetic moments. Additionally, Wannier functions were used to understand the experimentally observed rising trend in the Néel temperature, which is directly related to the magnetic exchange interaction paths in the materials. We suggest that out of layer M-O-P-O-M magnetic interactions (J⊥) are present in the studied materials. The current findings shed light on important differences observed in the electrochemistry of the cathode material LiCoPO4 compared to the already mature olivine material LiFePO4.

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“…In general, depending on the actual transition metal, LiM PO 4 develops long-range antiferromagnetic order at low temperatures and exhibits a large magneto-electric effect in the magnetically ordered phase [1,9,10]. The known magnetic phase diagrams of this family are rather complex, featuring incommensurate spin configurations, frustration, and usual magnetic excitations [11][12][13][14][15][16][17].…”

Section: Introductionmentioning

confidence: 99%

High magnetic field phase diagram and failure of the magnetic Grüneisen scaling in LiFePO4

et al. 2019

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We report the magnetic phase diagram of single-crystalline LiFePO 4 in magnetic fields up to 58 T and present a detailed study of magneto-elastic coupling by means of high-resolution capacitance dilatometry. Large anomalies at T N in the thermal expansion coefficient α imply pronounced magneto-elastic coupling. Quantitative analysis yields the magnetic Grüneisen parameter γ mag = 6.7(5) · 10 −7 mol/J. The positive hydrostatic pressure dependence dT N /dp = 1.46(11) K/GPa is dominated by uniaxial effects along the a-axis. Failure of Grüneisen scaling below ≈ 40 K, i.e., below the peak temperature in the magneto-electric coupling coefficient [1], implies several competing degrees of freedom and indicates relevance of recently observed hybrid excitations [2].A broad and strongly magnetic-field-dependent anomaly in α in this temperature regime highlight the relevance of structure changes. Upon application of magnetic fields B||b-axis, a pronounced jump in the magnetisation implies spin-reorientation at B SF = 32 T as well as a precursing phase at 29 T and T = 1.5 K. In a two-sublattice mean-field model, the saturation field B sat,b = 64(2) T enables the determination of the effective antiferromagnetic exchange interaction J af = 2.68(5) meV as well as the anisotropies D b = −0.53(4) meV and D c = 0.44(8) meV. PACS numbers:In addition to exceptionally high applicability of lithium orthophosphates [3][4][5] for electrochemical energy storage in Li-ion batteries, competing magnetic interactions, magnetic anisotropy and coupling of spin and electric degrees of freedom yield complex magnetic behaviour in LiM PO 4 (M = Mn, Fe, Co, Ni). The rich resulting physics is, e.g., demonstrated by ferrotoroidicity in LiCoPO 4 and LiNiPO 4 [6-8]. In general, depending on the actual transition metal, LiM PO 4 develops long-range antiferromagnetic order at low temperatures and exhibits a large magneto-electric effect in the magnetically ordered phase [1, 9, 10]. The known magnetic phase diagrams of this family are rather complex, featuring incommensurate spin configurations, frustration, and usual magnetic excitations [11-17]. Magnetic phase diagrams have been reported for all lithium orthophosphates [15-17] except for LiFePO 4 . At B = 0 T, LiFePO 4 develops long-range antiferromagnetic order of S = 2 spins of the magnetic Fe 2+ -ions below T N = 50 K [18]. The ordered moment amounts to 4.09 µ B [1, 19] and the spins are mainly directed along the crystallographic b-axis (space group P nma) [19]. Notably, the ground state features a collinear rotation of the spins towards the a-axis as well as spin canting along the c-axis with an overall rotation of the ordered moments of 1.3(1) • off the b-axis [1, 2]. The observed spin canting suggests the presence of Dzyaloshinsky-Moriya (DM) interactions which may account for the magneto-electric coupling in LiFePO 4 . In particular, as spin canting is not compatible with P nma symmetry, a lower crystal symmetry might appear below T N [ 1,20]. Even in the absence of spin canting, an alternative me...

show abstract

Unusual spin fluctuations and magnetic frustration in olivine and non-olivine LiCoPO4detected byP31and
S.‐H. Baek
¹
,
R. Klingeler
²
,
Christoph Neef
³

et al.

Cited by 10 publications

References 35 publications

Direct synthesis and characterization of mixed-valent Li_0.5−δCoPO₄, a Li-deficient derivative of the Cmcm polymorph of LiCoPO₄

Direct synthesis and characterization of mixed-valent Li_0.5−δCoPO₄, a Li-deficient derivative of the Cmcm polymorph of LiCoPO₄

Magnetism in olivine-type LiCo_1−xFe_xPO₄cathode materials: bridging theory and experiment

High magnetic field phase diagram and failure of the magnetic Grüneisen scaling in LiFePO4

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Unusual spin fluctuations and magnetic frustration in olivine and non-olivine LiCoPO4detected byP31andS.‐H. Baek1, R. Klingeler2, Christoph Neef3 et al.

Cited by 10 publications

References 35 publications

Direct synthesis and characterization of mixed-valent Li0.5−δCoPO4, a Li-deficient derivative of the Cmcm polymorph of LiCoPO4

Direct synthesis and characterization of mixed-valent Li0.5−δCoPO4, a Li-deficient derivative of the Cmcm polymorph of LiCoPO4

Magnetism in olivine-type LiCo1−xFexPO4cathode materials: bridging theory and experiment

High magnetic field phase diagram and failure of the magnetic Grüneisen scaling in LiFePO4

Contact Info

Product

Resources

About

Unusual spin fluctuations and magnetic frustration in olivine and non-olivine LiCoPO4detected byP31and
S.‐H. Baek
¹
,
R. Klingeler
²
,
Christoph Neef
³

et al.

Direct synthesis and characterization of mixed-valent Li_0.5−δCoPO₄, a Li-deficient derivative of the Cmcm polymorph of LiCoPO₄

Direct synthesis and characterization of mixed-valent Li_0.5−δCoPO₄, a Li-deficient derivative of the Cmcm polymorph of LiCoPO₄

Magnetism in olivine-type LiCo_1−xFe_xPO₄cathode materials: bridging theory and experiment