Cooling and heating modes are shown to be able to significantly modify the magnetic and electrical properties of the half-doped perovskite manganite.The present paper reports on a precise investigation of this phenome...Cooling and heating modes are shown to be able to significantly modify the magnetic and electrical properties of the half-doped perovskite manganite.The present paper reports on a precise investigation of this phenomenon(the so-called training effect) carried out on Nd0.5Ca0.5MnO3 manganite,which allow a fine tuning of the magnetic ground state.Refinement of the X-ray diffraction pattern shows that the synthesized sample is single phase and crystallizes in the orthorhombic structure with Pnma space group.Using magnetometry measurements,we have found that the sample is the seat of interesting phenomena like charge ordering,magnetic phase separation,spin-glass and inverse magnetocaloric effect.Magnetic-field-driven magnetization(M(μ0 H)) measurements evidence the metamagnetic transition which not only depends on field value,but also on the thermal process(cooling or heating).Metamagnetic irreversibility in the magnetic field range(±5 T) and memory effect are observed at low temperatures due to the kinetic arrest phenomenon.It is worthwhile to mention that the coercive field increases with decreasing temperature and reaches 955 Oe at 20 K,which is sufficiently large compared with that one in the soft magnetic and makes the material quite interesting for spintronic applications.The electrical resistivity in a zero field was measured on both cooling and warming modes,and the data obtained were fitted by using different theoretical models.At low temperatures,the resistivity shows the presence of insulator-metal transition and is found to be in conformity with the magnetization data.A magnetic training effect due to the thermo-magnetic history dependent behavior is observed,where the resistivity is consistently irreversible.展开更多
Polycrystalline samples of La0.4Cao.6Mn1-xCrxO3 （x = 0.00, 0.02, 0.04, 0.06） were prepared by the solid state reaction method. The influence of Cr3＋ substitution for Mn3＋ on the magnetic property and charge orderi...Polycrystalline samples of La0.4Cao.6Mn1-xCrxO3 （x = 0.00, 0.02, 0.04, 0.06） were prepared by the solid state reaction method. The influence of Cr3＋ substitution for Mn3＋ on the magnetic property and charge ordering phase of La0.4Ca0.6MnO3 was studied through the measurements of X-ray diffraction （XRD）, magnetization-temperature （M-T） curves and electron spin resonance （ESR） spectra. The experimental results indicate that the mother＇s body of La0.4Ca0.6MnO3 has very complicated magnetic structure, exhibits charge ordering phase at 258 K, and shows long-range strongly correlated charge ordering-antiferromagnetism （CO-AFM） phase from 175 to 50 K. Spin glass state appears when the temperature decreases to about 41 K. When the Cr substitution amount is x = 0.06, the charge ordering phase of the mother＇s body is de-stroyed, because the Cr3＋ substitution for Mn3＋ destroys the spin order of CE-type antiferromagnetism, and thus leads to the melting of charge ordering. It is verified experimentally that the strong coupling between charge order and spin order exists in the charge order system of CE-type antiferromagnetism.展开更多
文摘Cooling and heating modes are shown to be able to significantly modify the magnetic and electrical properties of the half-doped perovskite manganite.The present paper reports on a precise investigation of this phenomenon(the so-called training effect) carried out on Nd0.5Ca0.5MnO3 manganite,which allow a fine tuning of the magnetic ground state.Refinement of the X-ray diffraction pattern shows that the synthesized sample is single phase and crystallizes in the orthorhombic structure with Pnma space group.Using magnetometry measurements,we have found that the sample is the seat of interesting phenomena like charge ordering,magnetic phase separation,spin-glass and inverse magnetocaloric effect.Magnetic-field-driven magnetization(M(μ0 H)) measurements evidence the metamagnetic transition which not only depends on field value,but also on the thermal process(cooling or heating).Metamagnetic irreversibility in the magnetic field range(±5 T) and memory effect are observed at low temperatures due to the kinetic arrest phenomenon.It is worthwhile to mention that the coercive field increases with decreasing temperature and reaches 955 Oe at 20 K,which is sufficiently large compared with that one in the soft magnetic and makes the material quite interesting for spintronic applications.The electrical resistivity in a zero field was measured on both cooling and warming modes,and the data obtained were fitted by using different theoretical models.At low temperatures,the resistivity shows the presence of insulator-metal transition and is found to be in conformity with the magnetization data.A magnetic training effect due to the thermo-magnetic history dependent behavior is observed,where the resistivity is consistently irreversible.
基金supported by the Key Program of the National Natural Science Foundation of China (No.19934003)the Key Program of Natural Science Research of Anhui Education Department (No.KJ2011A259+3 种基金 KJ2008A34ZC)the Natural Science Research Programs of Anhui Education Department, China (No.KJ2010B229No.KJ2010B228No.KJ2009B281Z)
文摘Polycrystalline samples of La0.4Cao.6Mn1-xCrxO3 （x = 0.00, 0.02, 0.04, 0.06） were prepared by the solid state reaction method. The influence of Cr3＋ substitution for Mn3＋ on the magnetic property and charge ordering phase of La0.4Ca0.6MnO3 was studied through the measurements of X-ray diffraction （XRD）, magnetization-temperature （M-T） curves and electron spin resonance （ESR） spectra. The experimental results indicate that the mother＇s body of La0.4Ca0.6MnO3 has very complicated magnetic structure, exhibits charge ordering phase at 258 K, and shows long-range strongly correlated charge ordering-antiferromagnetism （CO-AFM） phase from 175 to 50 K. Spin glass state appears when the temperature decreases to about 41 K. When the Cr substitution amount is x = 0.06, the charge ordering phase of the mother＇s body is de-stroyed, because the Cr3＋ substitution for Mn3＋ destroys the spin order of CE-type antiferromagnetism, and thus leads to the melting of charge ordering. It is verified experimentally that the strong coupling between charge order and spin order exists in the charge order system of CE-type antiferromagnetism.
