| The physical properties in low dimensional transition metal oxides have become an important subject in condensed matter physics. As candidate materials of low dimensional transition metal oxides, quasi-one-dimensional spin chain system, Ca3Co2O6 and its related compounds have been widely studied in recent years. Due to the correlation between special low dimensional crystal structure and spin, these compounds exhibit a series of complex magnetic properties, e.g.1/3 magnetization step, incommensurate magnetic structure and ferroelectric polarization and so on. However, most of the interpretation for the complex magnetic properties in Ca3Co2O6 and its related compounds are self-consistent with the special experiments. Hence, the ground state magnetic properties and their original are still unsolved. In this thesis, we first study the complex magnetic properties and origin of them by metal ions-doping. Through the complex results we continue to do some deep research. The main investigations of this thesis are as follows.In the first part, a brief introduction about the research situation of Ca3Co2O6 and its related compounds were presented. Then we introduced the crystal structure, electronic configuration and magnetic structure of Ca3Co2O6 and its related compounds. The paramagnetic and low temperature magnetic properties of these compounds were discussed, respectively. From the discussion, we got the interest problems about the complex magnetic properties and their origins in this system at present.In the second part, a detailed introduction about the high pulsed field magnetic measurement platform was presented. Among this platform, we focused on the high field electronic spin resonance (ESR) system and magnetization measurement system. In the ESR system, the theory principle, development history and system configuration were emphasized. In the high pulsed magnetic field magnetization measurement system, the fabrication of the sample holder and the related circuit were mainly discussed.In the third part, in order to have a systematic investigation about the influence to the magnetic property in Ca3Co2O6 by ion doping, we first investigated the nonmagnetic Sc3+ ion and magnetic Mn4+ ion doped compounds by theoretical computing and magnetic experiments. The results demonstrate that the intrachain ferromagnetic (FM) interaction in is not much modified by nonmagnetic Sc3+ ion doping. The dominant interaction in this system is still FM interaction. While for the magnetic Mn4+ ion doping, the FM interaction is suppressed and disappeared by Mn-doping, the dominant interaction in this system is AFM interaction finally.In the fourth part, since a series of complex magnetic properties were presented in Mn-doped compounds, which also lead to ferroelectricity, we continue to do some deep investigation about the Mn-doped compounds. At low temperature, the Mn-doped compounds exhibit the spin glass effect different with Ca3Co2O6, so, by preparing single crystal Ca3Co1.62Mn0.38O6 and investigating its magnetic memory effect, we investigated spin glass effect and its origin. Amazing magnetic memory effect has been illustrated in Ca3Co1.62Mn0.38O6 by systematic magnetization measurements. The observed memory effect can be described by the phenomenological hierarchical model and its origin is associated with the chemical disorder by Mn4+ ions doping and competing antiferromagnetic and ferromagnetic interactions.In the fifth part, since the magnetic property control mechanism of Mn-doped compounds is considered to be the AFM spin arrangement in the spin chain or Ising characteristic changing by Mn doping, which do not have a certain improvement yet. Meanwhile, whether the exchange interaction model in Ca3CoMnO6 is J1-J2 model or dimer model still has some arguments. Hence, we performed high-field magnetization and ESR studies of Mn-doped compounds to investigate its spin ground state. The magnetic results demonstrate two metamagnetic transition within the Mn composition range of x=0.8-1.0 associated with spin configuration changes from zero-field ↑↑↓↓ to ↑↑↓↑ with the spin chain. For x< 0.8, however, presenting a single metamagnetic transition, which can be understood as ↑↑↓↑ to ↑↑↑↑ transition. High-field ESR measurements exhibit four different resonance modes with spin gap. These zero-field spin gaps are considered to be related with the spin dimer effect.In the sixth part, since the ferroelectricity in Ca3CoMnO6 is associated with its Ising nature and the Mn4+ ion is improved, which had no effect on the Ising nature, we use nonmagnetic Zn2+ doping the Co site in Ca3CoMnO6 to investigate its Ising nature for the first time. The experiment results suggest that the antiferromagntic resonance (AFMR) modes under Neel temperature of Ca3ZnMnO6 can be explained by conventional AFMR theory with easy-plane-anisotropy. The disappearance of the Ising nature in Ca3ZnMnO6 demonstrates the Co4+ ion in Ca3CoMnO6 plays an important role for the Ising nature. |
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