Spin Dynamics and Ground State of the Frustrated Diamond Lattice Magnet CoAl<inf>2</inf>O<inf>4</inf> as seen by ²⁷Al NMR

© 2016, Springer-Verlag Wien.We report an experimental study of the low-temperature dynamics of electron spin fluctuations in the magnetically frustrated spinel CoAl2O4 as revealed by 27Al nuclear magnetic relaxation measurements in a magnetic field of 7.7 T in the temperature range 4 < T < 240 K. With this local probe technique, we show that the dynamics of the correlated Co spins strongly depends on the frustration of spin interactions and on Co/Al site disorder. The anisotropy of the temperature dependences of the spin–lattice (T1−1) and spin–spin (T2−1) 27Al nuclear relaxation rates reveals a coexistence of the short-range Néel order below a characteristic temperature T* = 8 K and slow non-commensurate magnetic correlations below and above T*, in agreement with the results of neutron diffraction experiments and our previous NMR spectroscopy data

Enhanced Cooperation in an Asymmetric Model of Tax Competition

This paper analyzes enhanced cooperation agreements in corporate taxation in a three country tax competition model where countries differ in size. We characterize equilibrium tax rates and the optimal tax responses due to the formation of an enhanced cooperation agreement. Conditions for strategic complementarity or strategic substitutability of tax rates are crucial for the welfare effects of enhanced cooperation. Simulations show that enhanced cooperation is unlikely to be feasible for small countries. When enhanced cooperation is feasible, it may hamper global harmonization. Only when countries are of similar size is global harmonization a feasible outcome

Spin Dynamics and Ground State of the Frustrated Diamond Lattice Magnet CoAl<inf>2</inf>O<inf>4</inf> as seen by ²⁷Al NMR

© 2016, Springer-Verlag Wien.We report an experimental study of the low-temperature dynamics of electron spin fluctuations in the magnetically frustrated spinel CoAl2O4 as revealed by 27Al nuclear magnetic relaxation measurements in a magnetic field of 7.7 T in the temperature range 4 < T < 240 K. With this local probe technique, we show that the dynamics of the correlated Co spins strongly depends on the frustration of spin interactions and on Co/Al site disorder. The anisotropy of the temperature dependences of the spin–lattice (T1−1) and spin–spin (T2−1) 27Al nuclear relaxation rates reveals a coexistence of the short-range Néel order below a characteristic temperature T* = 8 K and slow non-commensurate magnetic correlations below and above T*, in agreement with the results of neutron diffraction experiments and our previous NMR spectroscopy data

Spin Dynamics and Ground State of the Frustrated Diamond Lattice Magnet CoAl<inf>2</inf>O<inf>4</inf> as seen by ²⁷Al NMR

© 2016, Springer-Verlag Wien.We report an experimental study of the low-temperature dynamics of electron spin fluctuations in the magnetically frustrated spinel CoAl2O4 as revealed by 27Al nuclear magnetic relaxation measurements in a magnetic field of 7.7 T in the temperature range 4 < T < 240 K. With this local probe technique, we show that the dynamics of the correlated Co spins strongly depends on the frustration of spin interactions and on Co/Al site disorder. The anisotropy of the temperature dependences of the spin–lattice (T1−1) and spin–spin (T2−1) 27Al nuclear relaxation rates reveals a coexistence of the short-range Néel order below a characteristic temperature T* = 8 K and slow non-commensurate magnetic correlations below and above T*, in agreement with the results of neutron diffraction experiments and our previous NMR spectroscopy data

Spin Dynamics and Ground State of the Frustrated Diamond Lattice Magnet CoAl<inf>2</inf>O<inf>4</inf> as seen by ²⁷Al NMR

© 2016, Springer-Verlag Wien.We report an experimental study of the low-temperature dynamics of electron spin fluctuations in the magnetically frustrated spinel CoAl2O4 as revealed by 27Al nuclear magnetic relaxation measurements in a magnetic field of 7.7 T in the temperature range 4 < T < 240 K. With this local probe technique, we show that the dynamics of the correlated Co spins strongly depends on the frustration of spin interactions and on Co/Al site disorder. The anisotropy of the temperature dependences of the spin–lattice (T1−1) and spin–spin (T2−1) 27Al nuclear relaxation rates reveals a coexistence of the short-range Néel order below a characteristic temperature T* = 8 K and slow non-commensurate magnetic correlations below and above T*, in agreement with the results of neutron diffraction experiments and our previous NMR spectroscopy data