Study On The Magnetic Properties Of Cr-doped Ni-X-Co Ferrite Nanomaterials

Nickel-cobalt-based ferrite was a ferrite magnetic material which is different from other general magnetic materials.As a ferrite nano-magnetic material with a spinel structure,it has very unique physical and chemical properties,especially mechanical properties,electrical properties,magnetism,optical and magnetic properties.Especially the magnetic properties represented by coercivity,magnetization,and magnetocrystalline anisotropy constant.The high coercivity,high frequency permeability,magnetocrystalline anisotropy constant,excellent chemical properties and corrosion resistance of the nickel-cobalt-based ferrite nano-magnetic material make the sample widely used in different fields:For example,in terms of magnetic recording materials,permanent magnets,wave-absorbing materials and gas-sensitive sensing materials,or as adsorbents and chromatographic fixatives.It can also be applied to biomedicine.The wide range of applications makes the performance requirements of nickel-cobalt-based ferrites more stringent.In this paper,Cr³⁺ion-doped Ni-Cu-Co ferrite nanomaterials and Ni-Mn-Co ferrite nanomaterials were prepared by sol-gel method,and their magnetic properties were analyzed and studied.The main work includes the following two parts:1.In this part,nickel nitrate,copper nitrate,cobalt nitrate,ferric nitrate were used as raw materials,citric acid was used as a complexing agent,and chromium nitrate was used as a modifier to synthesize Ni_0.2Cu_0.2Co_0.6Cr_xFe_2-xO₄by sol-gel method.The sample was characterized.The X-ray diffraction spectrum(XRD)data of the sample shows that the particle size range of the sample is 52.14-54.88 nm.The lattice constant varied is beween 8.3569(?)and 8.3758(?).Fourier infrared spectroscopy(FT-IR)data shows that the structure of the sample does not change with Cr ion doping,and can always remain a spinel type.It can be seen through the scanning electron microscope(SEM)that the morphology of the sample is irregular spherical.And because of the doping of chromium ions,it seems to have agglomeration phenomenon.The elements in the sample were analyzed by energy dispersive X-ray spectrometer(EDAX),and it was found that the sample contained Ni,Cu,Co,Fe,and O elements and a peak corresponding to the Cr element was found in the sample having crion content of 0.025,0.050,0.075 and 0.100.The magnetic properties of the samples were characterized using VSM.Process the data to obtain magnetic parameters such as saturation magnetization and coercivity.2.In this part,the sol-gel method is used to prepare a ferrite magnetic material with a nano-spinel structure with the chemical formula Ni_0.2Mn_0.1Co_0.7Cr_xFe_2-xO₄(x=0.000,0.025,0.050,0.075,0.100).Using XRD,Fourier Infrared,SEM,EDX,XPS to analyze the structure morphology and ion valence of the sample,it can be found that the maximum particle size of the sample can be achieved,and the minimum can be achieved.The lattice constant also changes with the doping of chromium ions,but the irregular spherical shape of the spinel structure is still maintained,and agglomeration occurs due to the local magnetism of the sample.And it can detect the corresponding peaks of elements such as nickel,manganese,cobalt,chromium,ferrite and different valence states,and using VSM to analyze the magnetic properties of the sample can find Ni_0.2Mn_0.1Co_0.7Cr_0.025Fe_1.975O₄when the chromium ion doping amount reaches 0.025.The sample has the best magnetic properties,whether it is saturation magnetization,residual magnetization,squareness ratio,or coercivity to coercivity squareness ratio.