chromium dioxide

• CAS: 12018-01-8
• Catalog Number: ACM12018018
• Category: Main Products
• Molecular Weight: 83.99
• Molecular Formula: CrO2
• Synonyms: Chromium oxide (CrO2)
• Appearance: Solid

Case Study

Magnetic Chromium Dioxide Nanoparticles for Enhancing Magnetorheological Response

Kim M H, et al. Smart Materials and Structures, 2017, 26(9), 095006.

Rod-shaped hard magnetic chromium dioxide nanoparticles were introduced as additives into soft magnetic carbonyl iron (CI)-based magnetorheological (MR) fluids, which effectively enhanced the MR properties and dispersion stability of the MR fluids.
Preparation and analysis of the MR fluid experimental system
· Soft magnetic CI particles (average diameter 4μm, density 7.79 g/cm) were used as magnetic response materials in this work. Silicone oil (viscosity 100 and 1000 cS) was used as the medium. Chromium dioxide (CrO2, density 5.12 g/cm3) with hard magnetic properties was used as an additive to improve the yield stress and dispersion stability. The experimental system of a MR fluid is composed of pristine CI (50 wt. %) and additive (0.5 wt. %) in the carrier oil with a stable dispersed state using a vortex and sonicator for 2 hours each.
· The nanoparticles' magnetic properties were examined using VSM, while the structural features resulting from filling potential cavities and coating CI particles with nanoparticles were verified through SEM analysis.
· Testing on a rotational rheometer under different magnetic field strengths confirmed the enhanced MR properties statically and dynamically. Both fluids, with and without the CrO2 additive, displayed typical MR characteristics indicative of Bingham fluid behavior. This suggests that the additives improve the MR performance.
· The relationship between magnetic field strength and dynamic yield stress was established using a universal scaling equation. Additionally, a dispersion stability test was conducted to demonstrate that the presence of nanoparticles reduces sedimentation in CI-based MR suspensions.

Neutron Diffraction Study of Chromium Dioxide Nanorods

Dho, Joonghoe, et al. Solid state communications, 2010, 150(1-2), 86-90.

To analyze the microstructure and magnetic properties of chromium dioxide (CrO2) nanorods, neutron diffraction experiments were performed at 3.5 K to 450 K. The experimental method involved collecting neutron diffraction data and conducting Rietveld analysis on CrO2 nanorods.
Microstructure and magnetic properties of CrO2 nanorods
· According to the Rietveld refinement analysis, it is suggested that each CrO2 nanorod likely consists of multiple microscopically oriented grains. Notably, the change in the ab lattice constants with temperature is more significant than that of the c lattice constant.
· Additionally, there is evidence of a distortion in CrO6 octahedra above the ferromagnetic transition of CrO2, which intensifies as the ferromagnetic order increases.
· The temperature-dependent resistivity data for the epitaxial CrO2/TiO2 film is closely related to the structural distortion around the ferromagnetic transition temperature. As the temperature decreases, a contraction of the apical bond of CrO6 octahedra perpendicular to the c-axis may lead to the localization of one electron into the lowest xy orbital and the occupation of the mixed (yz±zx) orbitals by another itinerant electron. This mechanism is believed to be responsible for inducing the half-metallic ferromagnetism in CrO2.

Ferromagnetic, Magnetotransport and Anisotropic Conductive Properties of Chromium Dioxide Thin Films

Gupta, A., Li, X. W., & Xiao, G. Journal of Applied Physics 87.9 (2000): 6073-6078.

The chemical composition, crystal structure and functional properties of epitaxial and polycrystalline chromium dioxide (CrO2 ) thin films were studied using X-ray diffraction (XRD), Rutherford backscattering spectroscopy (RBS), superconducting quantum interference device (SQUID) magnetometry, four-probe resistivity measurements, and atomic force microscopy (AFM). The films were grown via chemical vapor deposition (CVD) using CrO3 as the precursor: epitaxial films on single-crystal TiO2 (100) substrates, and polycrystalline films on polycrystalline TiO2 substrates or TiO2 seed layers on oxidized silicon. The CrO2 films consist of Cr4+ ions with a magnetic moment of 2 μB per ion, crystallizing in a rutile structure with high phase purity.
Chromium dioxide exhibited significant ferromagnetic properties: both epitaxial and polycrystalline films had a Curie temperature (TC ) of 390-395 K, with a saturation magnetization of ~650 emu/cm³ at low temperatures (consistent with the theoretical moment of 2 μB per Cr ion). Epitaxial CrO2 (100) films showed in-plane uniaxial magnetic anisotropy, with the c-axis as the magnetic easy axis (100% remanence) and coercive field (Hc ) of 15 Oe, while polycrystalline films had a rounded hysteresis loop with Hc ~40 Oe. It demonstrated distinct magnetotransport behavior: epitaxial films exhibited metallic conductivity (resistivity 250 μΩcm at room temperature, decreasing to 2.15 μΩcm at 2 K along the c-axis) with positive transverse magnetoresistance (MR) of 25% at 5 K (40 kOe) and negative MR of 7% near TC (380 K). Polycrystalline films were semiconducting (grain boundary-dominated resistance) with negative MR of 15% at 4.2 K (40 kOe) and a significant low-field hysteretic MR component attributed to spin-polarized grain boundary transport. Additionally, epitaxial films showed in-plane resistivity anisotropy, with lower room-temperature resistivity along the b-axis (177 μΩcm) compared to the c-axis. These studies demonstrate that chromium dioxide thin films possess significant ferromagnetic, magnetotransport, and anisotropic conductive properties.
The in vitro magnetic properties were characterized via SQUID magnetometry (hysteresis loops, temperature-dependent magnetization) and AFM (surface morphology/grain size). Transport properties (resistivity, MR) were measured using the four-probe dc method on selectively grown patterned films (50 μm wide, 200 μm long), with magnetic fields applied in-plane (parallel/perpendicular to current). Structural characterization included XRD (phase confirmation), RBS channeling (crystalline quality, χmin =1.7% for epitaxial films), and AFM (epitaxial film roughness ~40 Å, polycrystalline film grain size 2000-3000 Å). The results verified that film crystallinity (epitaxial vs. polycrystalline) strongly modulates magnetic anisotropy and transport behavior, making CrO2 suitable for spin-electronic and magnetic storage applications.

Pressure-Induced Structural Transition, Ferromagnetic and Half-Metallic Properties of Chromium Dioxide

Kuznetsov, A. Y., de Almeida, J. S., Dubrovinsky, L., Ahuja, R., Kwon, S. K., Kantor, I., Kantor, A., & Guignot, N. Journal of Applied Physics 99.5 (2006): 053909.

The chemical composition, high-pressure structural evolution and functional properties of chromium dioxide (CrO2 ) were studied using diamond anvil cell (DAC) synthesis, synchrotron X-ray diffraction (XRD), Raman spectroscopy, scanning electron microscopy-energy dispersive spectroscopy (SEM-EDS), and first-principles density functional theory (DFT) calculations. The CrO2 was synthesized via direct combustion of Cr and O2 (with/without N2 as a reaction promoter) under high pressure (14-37 GPa) and laser heating (≈2000 K). Two polymorphs were identified: tetragonal rutile-type (space group P42 /mnm) at ambient pressure and orthorhombic CaCl2 -type (space group Pnnm) at high pressure, with Cr4+ ions as the core cationic species.
Chromium dioxide exhibited significant pressure-induced structural transition behavior: a reversible rutile-to-CaCl2 -type phase transition occurred at ≈17 GPa, confirmed by XRD (splitting of h=k diffraction peaks) and Raman spectroscopy (splitting of degenerated Eg phonon mode into B2g and B3g modes). The orthorhombic phase had lattice parameters , , at 23 GPa, and reverted to the tetragonal phase upon decompression to 2 GPa. It maintained robust ferromagnetic properties across the phase transition: DFT calculations confirmed both polymorphs are ferromagnetic (FM) with a magnetic moment of 2 μB per formula unit, and ferromagnetism persisted up to 56 GPa. Additionally, CrO2 retained half-metallic characteristics in the orthorhombic phase, with the Fermi level lying in the gap of minority-spin bands and crossing the majority-spin conduction band. A ferromagnetic-to-paramagnetic (PM) transition was predicted at ≈53 GPa due to minority-spin band crossing the Fermi level, without affecting its metallic nature. These studies demonstrate that chromium dioxide possesses significant pressure-induced structural transition, ferromagnetic, and half-metallic properties.
The in vitro structural and magnetic properties were investigated via in situ high-pressure XRD (ESRF ID30 beamline) and Raman spectroscopy (LabRAM/Dilor XY systems) during compression/decompression cycles. Synthesis was conducted in DAC with laser heating, and phase purity was verified by SEM-EDS (Cr:O stoichiometry ≈1:2). DFT calculations (VASP code, GGA-PW91) were used to simulate total energy, enthalpy, and density of states (DOS) for both phases. Pressure calibration was performed via ruby fluorescence spectroscopy. The results verified that the pressure-induced structural transition modifies lattice symmetry but preserves ferromagnetism and half-metallicity, expanding the potential of CrO2 in high-pressure spin-electronic devices.

Custom Q&A

What is the molecular formula of Magtrieve(TM)?

The molecular formula of Magtrieve(TM) is CrH4O2.

What is the PubChem CID of Magtrieve(TM)?

The PubChem CID of Magtrieve(TM) is 15972932.

What is the molecular weight of Magtrieve(TM)?

The molecular weight of Magtrieve(TM) is 88.027 g/mol.

What are the synonyms of Magtrieve(TM)?

The synonyms of Magtrieve(TM) are "Magtrieve(TM) chromium;dihydrate" and "12018-01-8".

When was Magtrieve(TM) last modified?

Magtrieve(TM) was last modified on December 2, 2023.

What is the IUPAC name of Magtrieve(TM)?

The IUPAC name of Magtrieve(TM) is chromium;dihydrate.

What is the InChI of Magtrieve(TM)?

The InChI of Magtrieve(TM) is InChI=1S/Cr.2H2O/h;2*1H2.

What is the InChIKey of Magtrieve(TM)?

The InChIKey of Magtrieve(TM) is DJCIVHDYINPEKO-UHFFFAOYSA-N.

How many hydrogen bond donor counts does Magtrieve(TM) have?

Magtrieve(TM) has 2 hydrogen bond donor counts.

Does Magtrieve(TM) have a defined bond stereocenter count?

No, Magtrieve(TM) does not have a defined bond stereocenter count.