In spin‐gapped quasi‐one‐dimensional antiferromagnets that do not show phase transitions down to zero temperature, impurities cause phase transitions by inducing local magnetic moments around them between which long‐range correlation is mediated by weak interchain couplings. We investigate the difference between the effects of non‐magnetic impurities and those of spin‐1/2 magnetic ones in the impurity‐induced transition temperatures and the staggered magnetization in the impurity‐induced ordered phase by the quantum Monte Carlo method. We find that the staggered correlation induced by spin‐1/2 impurities grows slower than that done by non‐magnetic ones as the system is cooled and approaches the ground state, while the transition temperature induced by the former is higher than that done by the latter. We argue that this is one of the characteristic aspects of the order‐by‐disorder phenomena in quantum systems.In spin‐gapped quasi‐one‐dimensional antiferromagnets that do not show phase transitions down to zero temperature, impurities cause phase transitions by inducing local magnetic moments around them between which long‐range correlation is mediated by weak interchain couplings. We investigate the difference between the effects of non‐magnetic impurities and those of spin‐1/2 magnetic ones in the impurity‐induced transition temperatures and the staggered magnetization in the impurity‐induced ordered phase by the quantum Monte Carlo method. We find that the staggered correlation induced by spin‐1/2 impurities grows slower than that done by non‐magnetic ones as the system is cooled and approaches the ground state, while the transition temperature induced by the former is higher than that done by the latter. We argue that this is one of the characteristic aspects of the order‐by‐disorder phenomena in quantum systems.

AIP conference proceedingsJan 1, 20060 citations

Quantum Phase Transitions in Models of Magnetic Impurities

R. Bulla, Matthias Vojta C

Springer eBooksJan 1, 20036 citations

Quantum Phase Transitions in Random Magnets

R. N. Bhatt

Springer proceedings in physicsJan 1, 19980 citations

Impurity effects in coupled-ladder BiCu2PO6 studied by NMR and quantum Monte Carlo simulations

Libu K. Alexander, Julien Bobroff, A. V. Mahajan +3 more

We present a $^{31}\text{P}$ NMR study of the coupled spin $\frac{1}{2}$ ladder compound ${\text{BiCu}}_{2}{\text{PO}}_{6}$ . In the pure material, intrinsic susceptibility, and dynamics show a spin gap of about $\ensuremath{\Delta}\ensuremath{\approx}35--40\text{ }\text{K}$. Substitution of nonmagnetic Zn or magnetic Ni impurity at Cu site induces a staggered magnetization which results in a broadening of the $^{31}\text{P}$ NMR line while susceptibility far from the defects is unaffected. The effect of Ni on the NMR line broadening is twice that of Zn, which is consistent with quantum Monte Carlo calculations assuming that Ni couples ferromagnetically to its adjacent Cu. The induced moment follows a $1/T$ temperature dependence due to the Curie-type development of the moment amplitude while its extension saturates and does not depend on impurity content or nature. This allow us to verify the generically expected scenario for impurity doping and to extend it to magnetic impurity case: in an antiferromagnetically correlated low-dimensional spin system with antiferromagnetic correlations, any type of impurity induces a staggered moment at low temperature, whose extension is not linked to the impurity nature but to the intrinsic physics at play in the undoped pure system, from one-dimensional to two-dimensional systems.We present a $^{31}\text{P}$ NMR study of the coupled spin $\frac{1}{2}$ ladder compound ${\text{BiCu}}_{2}{\text{PO}}_{6}$. In the pure material, intrinsic susceptibility, and dynamics show a spin gap of about $\ensuremath{\Delta}\ensuremath{\approx}35--40\text{ }\text{K}$. Substitution of nonmagnetic Zn or magnetic Ni impurity at Cu site induces a staggered magnetization which results in a broadening of the $^{31}\text{P}$ NMR line while susceptibility far from the defects is unaffected. The effect of Ni on the NMR line broadening is twice that of Zn, which is consistent with quantum Monte Carlo calculations assuming that Ni couples ferromagnetically to its adjacent Cu. The induced moment follows a $1/T$ temperature dependence due to the Curie-type development of the moment amplitude while its extension saturates and does not depend on impurity content or nature. This allow us to verify the generically expected scenario for impurity doping and to extend it to magnetic impurity case: in an antiferromagnetically correlated low-dimensional spin system with antiferromagnetic correlations, any type of impurity induces a staggered moment at low temperature, whose extension is not linked to the impurity nature but to the intrinsic physics at play in the undoped pure system, from one-dimensional to two-dimensional systems.

arXiv:0912.4353Physical Review BFeb 24, 201026 citations

Influence of Quenched Non-Magnetic Impurities on Phase Transitions in Low-Dimensional Potts Models

Akai Kurbanovich Murtazaev, Albert Babaevich Babaev

Abstract The effect of quenched non-magnetic impurities on phase transitions in low-dimensional Potts model structures is investigated by the Monte Carlo method using a cluster algorithm. Systems with linear dimensions of L = 20–160 and spin concentrations of p = 1.0, 0.9 are considered. Using the fourth-order Binder cumulant method and the histogram-data analysis method, the introduction of weak quenched disorder (p = 0.9) in the form of non-magnetic impurities is shown to change the order of the phase transition from the first to the second.Abstract The effect of quenched non-magnetic impurities on phase transitions in low-dimensional Potts model structures is investigated by the Monte Carlo method using a cluster algorithm. Systems with linear dimensions of L = 20–160 and spin concentrations of p = 1.0, 0.9 are considered. Using the fourth-order Binder cumulant method and the histogram-data analysis method, the introduction of weak quenched disorder (p = 0.9) in the form of non-magnetic impurities is shown to change the order of the phase transition from the first to the second.

Journal of Surface Investigation X-ray Synchrotron and Neutron TechniquesJul 1, 20203 citations

Quantum phase transitions in random magnets

A. P. Young

Journal of Magnetism and Magnetic MaterialsMay 1, 20012 citations

We present a

^{31}\text{P}

NMR study of the coupled spin

\frac{1}{2}

ladder compound

{\text{BiCu}}_{2}{\text{PO}}_{6}

. In the pure material, intrinsic susceptibility, and dynamics show a spin gap of about $\ensuremath{\Delta}\ensuremath{\approx}35--40\text{ }\text{K}$. Substitution of nonmagnetic Zn or magnetic Ni impurity at Cu site induces a staggered magnetization which results in a broadening of the

^{31}\text{P}

NMR line while susceptibility far from the defects is unaffected. The effect of Ni on the NMR line broadening is twice that of Zn, which is consistent with quantum Monte Carlo calculations assuming that Ni couples ferromagnetically to its adjacent Cu. The induced moment follows a

1/T

temperature dependence due to the Curie-type development of the moment amplitude while its extension saturates and does not depend on impurity content or nature. This allow us to verify the generically expected scenario for impurity doping and to extend it to magnetic impurity case: in an antiferromagnetically correlated low-dimensional spin system with antiferromagnetic correlations, any type of impurity induces a staggered moment at low temperature, whose extension is not linked to the impurity nature but to the intrinsic physics at play in the undoped pure system, from one-dimensional to two-dimensional systems.