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Spin – orbit coupled molecular quantum magnetism realized in inorganic solid

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ABSTRACT

Molecular quantum magnetism involving an isolated spin state is of particular interest due to the characteristic quantum phenomena underlying spin qubits or molecular spintronics for quantum information devices, as demonstrated in magnetic metal–organic molecular systems, the so-called molecular magnets. Here we report the molecular quantum magnetism realized in an inorganic solid Ba3Yb2Zn5O11 with spin–orbit coupled pseudospin-½ Yb3+ ions. The magnetization represents the magnetic quantum values of an isolated Yb4 tetrahedron with a total (pseudo)spin 0, 1 and 2. Inelastic neutron scattering results reveal that a large Dzyaloshinsky–Moriya interaction originating from strong spin–orbit coupling of Yb 4f is a key ingredient to explain magnetic excitations of the molecular magnet states. The Dzyaloshinsky–Moriya interaction allows a non-adiabatic quantum transition between avoided crossing energy levels, and also results in unexpected magnetic behaviours in conventional molecular magnets.

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Field-dependent INS spectra and evolution of excitation energies.(a) Constant-Q cuts I(ω)'s obtained by integrating measured I(Q,ω)'s over a range of 0.8 Å−1<Q<1.8 Å−1 at T=200 mK in external magnetic fields ranging from H=0 to H=10 T. Solid lines are obtained by fitting the experimental I(ω)'s with parameters of J, d and g-factors in . (b) Calculated excitation energy diagrams as a function of the H-field along the three principal axes [0 0 1], [1 1 0] and [1 1 1] are overlapped on the contour map of I(ω)'s. Excitation peak positions of I(ω)'s agree well with calculations. Peak intensites are presented by the grey scale bar. Selected three excitations, related to the level crossings at HC1 and HC2 are, respectively, marked with stars, diamonds and triangles in a and b. (c) Avoided level crossing along H//[1 1 0] near H=HC1 in a low-energy region. The colour scale bar represents the magnetization value <gSz> per Yb for the line colours in b and c. On the other hand, the avoided level crossing feature appears along H//[0 0 1] near H=HC2. Intensity error bars are square roots of intensities.
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f3: Field-dependent INS spectra and evolution of excitation energies.(a) Constant-Q cuts I(ω)'s obtained by integrating measured I(Q,ω)'s over a range of 0.8 Å−1<Q<1.8 Å−1 at T=200 mK in external magnetic fields ranging from H=0 to H=10 T. Solid lines are obtained by fitting the experimental I(ω)'s with parameters of J, d and g-factors in . (b) Calculated excitation energy diagrams as a function of the H-field along the three principal axes [0 0 1], [1 1 0] and [1 1 1] are overlapped on the contour map of I(ω)'s. Excitation peak positions of I(ω)'s agree well with calculations. Peak intensites are presented by the grey scale bar. Selected three excitations, related to the level crossings at HC1 and HC2 are, respectively, marked with stars, diamonds and triangles in a and b. (c) Avoided level crossing along H//[1 1 0] near H=HC1 in a low-energy region. The colour scale bar represents the magnetization value <gSz> per Yb for the line colours in b and c. On the other hand, the avoided level crossing feature appears along H//[0 0 1] near H=HC2. Intensity error bars are square roots of intensities.

Mentions: Validity of the effective Hamiltonian can be also confirmed in the field-dependent INS results at 200 mK. Figure 3a shows I(ω), integration of I(Q,ω) over 0.8 Å−1<Q<1.8 Å−1, under various external magnetic fields in comparison with the theoretical simulations. The excitation peaks evolve with the external field. The simulated I(ω) spectra represent spherically averaged I(ω) from exactly diagonalized . The simulations well reproduce the experiments with the g-factor values g//=2.62(2) and g∥=2.33(2), which are slightly smaller than the values obtained from the M(H) curve, likely due to an estimation error. These g-factor values are also consistent with the values estimated from the electron paramagnetic resonance spectrum and those determined from YbO6 CF analyses for reported high-energy neutron excitation spectra25 as discussed in Supplementary Notes 2 and 4, respectively.


Spin – orbit coupled molecular quantum magnetism realized in inorganic solid
Field-dependent INS spectra and evolution of excitation energies.(a) Constant-Q cuts I(ω)'s obtained by integrating measured I(Q,ω)'s over a range of 0.8 Å−1<Q<1.8 Å−1 at T=200 mK in external magnetic fields ranging from H=0 to H=10 T. Solid lines are obtained by fitting the experimental I(ω)'s with parameters of J, d and g-factors in . (b) Calculated excitation energy diagrams as a function of the H-field along the three principal axes [0 0 1], [1 1 0] and [1 1 1] are overlapped on the contour map of I(ω)'s. Excitation peak positions of I(ω)'s agree well with calculations. Peak intensites are presented by the grey scale bar. Selected three excitations, related to the level crossings at HC1 and HC2 are, respectively, marked with stars, diamonds and triangles in a and b. (c) Avoided level crossing along H//[1 1 0] near H=HC1 in a low-energy region. The colour scale bar represents the magnetization value <gSz> per Yb for the line colours in b and c. On the other hand, the avoided level crossing feature appears along H//[0 0 1] near H=HC2. Intensity error bars are square roots of intensities.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC5035996&req=5

f3: Field-dependent INS spectra and evolution of excitation energies.(a) Constant-Q cuts I(ω)'s obtained by integrating measured I(Q,ω)'s over a range of 0.8 Å−1<Q<1.8 Å−1 at T=200 mK in external magnetic fields ranging from H=0 to H=10 T. Solid lines are obtained by fitting the experimental I(ω)'s with parameters of J, d and g-factors in . (b) Calculated excitation energy diagrams as a function of the H-field along the three principal axes [0 0 1], [1 1 0] and [1 1 1] are overlapped on the contour map of I(ω)'s. Excitation peak positions of I(ω)'s agree well with calculations. Peak intensites are presented by the grey scale bar. Selected three excitations, related to the level crossings at HC1 and HC2 are, respectively, marked with stars, diamonds and triangles in a and b. (c) Avoided level crossing along H//[1 1 0] near H=HC1 in a low-energy region. The colour scale bar represents the magnetization value <gSz> per Yb for the line colours in b and c. On the other hand, the avoided level crossing feature appears along H//[0 0 1] near H=HC2. Intensity error bars are square roots of intensities.
Mentions: Validity of the effective Hamiltonian can be also confirmed in the field-dependent INS results at 200 mK. Figure 3a shows I(ω), integration of I(Q,ω) over 0.8 Å−1<Q<1.8 Å−1, under various external magnetic fields in comparison with the theoretical simulations. The excitation peaks evolve with the external field. The simulated I(ω) spectra represent spherically averaged I(ω) from exactly diagonalized . The simulations well reproduce the experiments with the g-factor values g//=2.62(2) and g∥=2.33(2), which are slightly smaller than the values obtained from the M(H) curve, likely due to an estimation error. These g-factor values are also consistent with the values estimated from the electron paramagnetic resonance spectrum and those determined from YbO6 CF analyses for reported high-energy neutron excitation spectra25 as discussed in Supplementary Notes 2 and 4, respectively.

View Article: PubMed Central - PubMed

ABSTRACT

Molecular quantum magnetism involving an isolated spin state is of particular interest due to the characteristic quantum phenomena underlying spin qubits or molecular spintronics for quantum information devices, as demonstrated in magnetic metal&ndash;organic molecular systems, the so-called molecular magnets. Here we report the molecular quantum magnetism realized in an inorganic solid Ba3Yb2Zn5O11 with spin&ndash;orbit coupled pseudospin-&frac12; Yb3+ ions. The magnetization represents the magnetic quantum values of an isolated Yb4 tetrahedron with a total (pseudo)spin 0, 1 and 2. Inelastic neutron scattering results reveal that a large Dzyaloshinsky&ndash;Moriya interaction originating from strong spin&ndash;orbit coupling of Yb 4f is a key ingredient to explain magnetic excitations of the molecular magnet states. The Dzyaloshinsky&ndash;Moriya interaction allows a non-adiabatic quantum transition between avoided crossing energy levels, and also results in unexpected magnetic behaviours in conventional molecular magnets.

No MeSH data available.


Related in: MedlinePlus