The metal–insulator transition in the strongly correlated layered compound Na CoO₂induced by dilute Mn doping

Abstract

Structure, transport and magnetic properties have been investigated for the layered materials Na γ Co 1−x Mn x O 2 (0 x 0.5). With increase of the Mn concentration, the in-plane lattice parameter a decreases while the lattice parameter c increases. 3% Mn doping can result in a metal-insulator transition. The temperature dependence of the magnetization of the samples obeys the Curie-Weiss law and the effective moment of the magnetic ions increases with doping. Electron energy-loss spectroscopy measurement shows that the Co valence is about 3.3 and remains unchanged upon doping. However, the valence of Mn increases rapidly with doping and reaches 3.7 ± 0.1 for the sample with x = 0.5. The results are discussed in terms of the disorder effect induced by doping of magnetic ions. This work demonstrates that the structure, transport and magnetic properties of Na γ CoO 2 are very sensitive to doping with magnetic ions.

Effect of Ti doping on the electrical transport and magnetic properties of layered compound Na0.8CoO2

“…From above discussion, it can be deduced that Mn doping tends to decrease R c and increase the real M-M distance. This will drive the system to become a semiconductor and this is supported by our previous work [7]. Ti doping makes the lattice parameter a of …”

“…In order to study the influence of the Ti doping on the valence states of Co in the doubt that a small amount of Ti doping leads to a metal-insulator transition, which is similar to that in NaCo 1-x Mn x O 2 [7]. It can be seen from the inset that the resistivity at the temperature of 15 K increases with the increase of x and an abrupt increase occurs at about x=0.07.…”

Synthesis, structure characterization and magnetic properties of nanosize LiCo1 − y Ni y O2 prepared by sol–gel citric acid route

“…In high temperature region, χ m shows a weak dependence on temperature. These results indicate that the magnetic property of delithiated LiCo 1−y Ni y O 2 is extraordinarily sensitive to the Ni doping at low temperatures, which can be interpreted by magnetic Ni 3+ or Ni 4+ substituting for nonmagnetic Co 3+ [25]. In addition, the two samples follow a Curie-Weiss behavior (Eq.…”

The Metal-Insulator Transition of Na0.8Co1-xSmxO2

“…Because of its particular properties of large thermoelectric power coexisting with low electrical resistivity, the sodium-cobalt oxide NaCoO 2 system has attracted much attention in recent years [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16]. Now in-depth study has uncovered a variety of anomalous nonFermi-liquid (NFL) behavior, which is thought to be engendered by strong interaction between the charge carriers in NaCoO 2 [7].…”

“…Subsequently, Yokoi et al presented that superconducting transition temperature Tc may be influenced by Ir substitution for Co, and reported that Na 0.75 Co 1-x Ir x O 2 sample becomes insulating when Ir content as small as 0.02 [10]. Zhang et al prepared the polycrystalline samples with nominal compositions NaCo 1-x Mn x O 2 and found that a low level doping with 3% Mn replacing Co leads to a metal-insulator transition [11]. Then, Ti, Ga, Ru, Ni, Zn and other substitution for Co in NaCoO 2 were investigated in succession [12][13][14][15][16].…”