scholarly journals Room Temperature Magnetic Memory Effect in Nanodiamond/γ-Fe2O3 Composites

Nanomaterials ◽  
2021 ◽  
Vol 11 (3) ◽  
pp. 648
Author(s):  
Ashish Chhaganlal Gandhi ◽  
Rajakar Selvam ◽  
Chia-Liang Cheng ◽  
Sheng Yun Wu
Keyword(s):  
Memory Effect ◽  
Room Temperature ◽  
Magnetic Measurements ◽  
Relaxation Times ◽  
Weight Fraction ◽  
Wide Distribution ◽  
Blocking Temperature ◽  
Magnetic Memory ◽  
Potential Applications ◽  
Fe2o3 Nanoparticle

We report a room temperature magnetic memory effect (RT-MME) from magnetic nanodiamond (MND) (ND)/γ-Fe2O3 nanocomposites. The detailed crystal structural analysis of the diluted MND was performed by synchrotron radiation X-ray diffraction, revealing the composite nature of MND having 99 and 1% weight fraction ND and γ-Fe2O3 phases, respectively. The magnetic measurements carried out using a DC SQUID magnetometer show the non-interacting superparamagnetic nature of γ-Fe2O3 nanoparticles in MND have a wide distribution in the blocking temperature. Using different temperature, field, and time relaxation protocols, the memory phenomenon in the DC magnetization has been observed at room temperature (RT). These findings suggest that the dynamics of MND are governed by a wide distribution of particle relaxation times, which arise from the distribution of γ-Fe2O3 nanoparticle size. The observed RT ferromagnetism coupled with MME in MND will find potential applications in ND-based spintronics.

Strong memory effect at room temperature in nanostructured granular alloy Co0.3Cu0.7

RSC Advances ◽  
2015 ◽  
Vol 5 (116) ◽  
pp. 95695-95702 ◽  
Author(s):  
S. Dhara ◽  
R. Roy Chowdhury ◽  
B. Bandyopadhyay
Keyword(s):  
Temperature Distribution ◽  
Memory Effect ◽  
Room Temperature ◽  
Blocking Temperature ◽  
Magnetic Memory

Non-interacting magnetic CoCu nanoparticles with a blocking temperature distribution show strong magnetic memory effect even at room temperature.

scholarly journals A Bis-Monophospholyl Dysprosium Cation Showing Magnetic Hysteresis at 48 Kelvin

2019 ◽  
Author(s):  
Peter Evans ◽  
Daniel Reta ◽  
George F. S. Whitehead ◽  
Nicholas Chilton ◽  
David Mills
Keyword(s):  
Data Storage ◽  
Single Molecule ◽  
Structural Changes ◽  
Elevated Temperatures ◽  
Spin Dynamics ◽  
Magnetic Hysteresis ◽  
Relaxation Times ◽  
Magnetic Memory ◽  
Relaxation Processes ◽  
Potential Applications

Single-molecule magnets (SMMs) have potential applications in high-density data storage, but magnetic relaxation times at elevated temperatures must be increased to make them practically useful. <i>Bis</i>-cyclopentadienyl lanthanide sandwich complexes have emerged as the leading candidates for SMMs that show magnetic memory at liquid nitrogen temperatures, but the relaxation mechanisms mediated by aromatic C<sub>5</sub> rings have not been fully established. Here we synthesise a <i>bis</i>-monophospholyl dysprosium SMM [Dy(Dtp)<sub>2</sub>][Al{OC(CF<sub>3</sub>)<sub>3</sub>}<sub>4</sub>] (<b>1</b>, Dtp = {P(C<sup>t</sup>BuCMe)<sub>2</sub>}) by the treatment of <i>in situ</i>-prepared “[Dy(Dtp)<sub>2</sub>(C<sub>3</sub>H<sub>5</sub>)]” with [HNEt<sub>3</sub>][Al{OC(CF<sub>3</sub>)<sub>3</sub>}<sub>4</sub>]. SQUID magnetometry reveals that <b>1</b> has an effective barrier to magnetisation reversal of 1,760 K (1,223 cm<sup>–1</sup>) and magnetic hysteresis up to 48 K. <i>Ab initio</i> calculation of the spin dynamics reveal that transitions out of the ground state are slower in <b>1</b> than in the first reported dysprosocenium SMM, [Dy(Cp<sup>ttt</sup>)<sub>2</sub>][B(C<sub>6</sub>F<sub>5</sub>)<sub>4</sub>] (Cp<sup>ttt</sup> = C<sub>5</sub>H<sub>2</sub><sup>t</sup>Bu<sub>3</sub>-1,2,4), however relaxation is faster in <b>1</b> overall due to the compression of electronic energies and to vibrational modes being brought on-resonance by the chemical and structural changes introduced by the <i>bis</i>-Dtp framework. With the preparation and analysis of <b>1</b> we are thus able to further refine our understanding of relaxation processes operating in <i>bis</i>-C<sub>5</sub>/C<sub>4</sub>P sandwich lanthanide SMMs, which is the necessary first step towards rationally achieving higher magnetic blocking temperatures in these systems in future.

Magnetic memory effect at room temperature in exchange coupled NiFe2O4-NiO nanogranular system

2017 ◽  
Vol 111 (18) ◽  
pp. 182406 ◽  
Author(s):  
Zhaoming Tian ◽  
Longmeng Xu ◽  
Yuxia Gao ◽  
Songliu Yuan ◽  
Zhengcai Xia
Keyword(s):  
Memory Effect ◽  
Room Temperature ◽  
Magnetic Memory

scholarly journals A Bis-Monophospholyl Dysprosium Cation Showing Magnetic Hysteresis at 48 Kelvin

2019 ◽  
Author(s):  
Peter Evans ◽  
Daniel Reta ◽  
George F. S. Whitehead ◽  
Nicholas Chilton ◽  
David Mills
Keyword(s):  
Data Storage ◽  
Single Molecule ◽  
Structural Changes ◽  
Elevated Temperatures ◽  
Spin Dynamics ◽  
Magnetic Hysteresis ◽  
Relaxation Times ◽  
Magnetic Memory ◽  
Relaxation Processes ◽  
Potential Applications

Single-molecule magnets (SMMs) have potential applications in high-density data storage, but magnetic relaxation times at elevated temperatures must be increased to make them practically useful. <i>Bis</i>-cyclopentadienyl lanthanide sandwich complexes have emerged as the leading candidates for SMMs that show magnetic memory at liquid nitrogen temperatures, but the relaxation mechanisms mediated by aromatic C<sub>5</sub> rings have not been fully established. Here we synthesise a <i>bis</i>-monophospholyl dysprosium SMM [Dy(Dtp)<sub>2</sub>][Al{OC(CF<sub>3</sub>)<sub>3</sub>}<sub>4</sub>] (<b>1</b>, Dtp = {P(C<sup>t</sup>BuCMe)<sub>2</sub>}) by the treatment of <i>in situ</i>-prepared “[Dy(Dtp)<sub>2</sub>(C<sub>3</sub>H<sub>5</sub>)]” with [HNEt<sub>3</sub>][Al{OC(CF<sub>3</sub>)<sub>3</sub>}<sub>4</sub>]. SQUID magnetometry reveals that <b>1</b> has an effective barrier to magnetisation reversal of 1,760 K (1,223 cm<sup>–1</sup>) and magnetic hysteresis up to 48 K. <i>Ab initio</i> calculation of the spin dynamics reveal that transitions out of the ground state are slower in <b>1</b> than in the first reported dysprosocenium SMM, [Dy(Cp<sup>ttt</sup>)<sub>2</sub>][B(C<sub>6</sub>F<sub>5</sub>)<sub>4</sub>] (Cp<sup>ttt</sup> = C<sub>5</sub>H<sub>2</sub><sup>t</sup>Bu<sub>3</sub>-1,2,4), however relaxation is faster in <b>1</b> overall due to the compression of electronic energies and to vibrational modes being brought on-resonance by the chemical and structural changes introduced by the <i>bis</i>-Dtp framework. With the preparation and analysis of <b>1</b> we are thus able to further refine our understanding of relaxation processes operating in <i>bis</i>-C<sub>5</sub>/C<sub>4</sub>P sandwich lanthanide SMMs, which is the necessary first step towards rationally achieving higher magnetic blocking temperatures in these systems in future.

Field pulse induced magnetic memory effect at room temperature in exchange coupled NiFe2O4/NiO nanocomposites

2019 ◽  
Vol 469 ◽  
pp. 504-509 ◽  
Author(s):  
Longmeng Xu ◽  
Yuxia Gao ◽  
Ashtar Malik ◽  
Yong Liu ◽  
Gaoshang Gong ◽  
...  
Keyword(s):  
Memory Effect ◽  
Room Temperature ◽  
Magnetic Memory ◽  
Field Pulse

Surface-spin driven room temperature magnetic memory effect in Fe-substituted NiO nanoparticles

2021 ◽  
Vol 536 ◽  
pp. 147856
Author(s):  
Ashish Chhaganlal Gandhi ◽  
Hsin-Hao Chiu ◽  
Kuan-Ting Wu ◽  
Chia-Liang Cheng ◽  
Sheng Yun Wu
Keyword(s):  
Memory Effect ◽  
Room Temperature ◽  
Magnetic Memory ◽  
Nio Nanoparticles ◽  
Surface Spin

Effect of Size Reduction on Structure, Magnetic Memory and Relaxation of La0.7Sr0.3MnO3 Nanowires

2019 ◽  
Vol 11 (11) ◽  
pp. 1104-1110
Author(s):  
Subarna Datta ◽  
Nilotpal Ghosh ◽  
Barnali Ghosh
Keyword(s):  
Memory Effect ◽  
Size Effects ◽  
Magnetic Relaxation ◽  
Relaxation Times ◽  
Finite Size ◽  
Magnetic Memory ◽  
Polymeric Precursor ◽  
Relaxation Measurement ◽  
Finite Size Effects ◽  
Precursor Route

We have demonstrated here the study of memory effect, relaxation and interaction of hydrothermally grown La0.7Sr0.3MnO3 (LSMO-0.3) nanowires (NWs) and its bulk form synthesized by using polymeric precursor route. Magnetic relaxation measurement has been performed and the analysis shows the existence of two relaxation times in both the cases. It has been observed that both the samples show signature of magnetic memory effect and prefer magnetized state. Curie temperature of La0.7Sr0.3MnO3 (LSMO-0.3) NWs is decreased compared to its bulk form due to finite size effects.

scholarly journals Room Temperature Magnetic Memory Effect in Cluster-Glassy Fe-Doped NiO Nanoparticles

Nanomaterials ◽  
2020 ◽  
Vol 10 (7) ◽  
pp. 1318 ◽  
Author(s):  
Ashish Chhaganlal Gandhi ◽  
Tai-Yue Li ◽  
B. Vijaya Kumar ◽  
P. Muralidhar Reddy ◽  
Jen-Chih Peng ◽  
...  
Keyword(s):  
Magnetic Moment ◽  
Room Temperature ◽  
Magnetic Measurements ◽  
Oxide System ◽  
Precipitation Method ◽  
Magnetic Memory ◽  
Nio Nanoparticles ◽  
Magnetic Anisotropy Energy ◽  
Spintronic Devices ◽  
Co Precipitation

The Fe-doped NiO nanoparticles that were synthesized using a co-precipitation method are characterized by enhanced room-temperature ferromagnetic property evident from magnetic measurements. Neutron powder diffraction experiments suggested an increment of the magnetic moment of 3d ions in the nanoparticles as a function of Fe-concentration. The temperature, time, and field-dependent magnetization measurements show that the effect of Fe-doping in NiO has enhanced the intraparticle interactions due to formed defect clusters. The intraparticle interactions are proposed to bring additional magnetic anisotropy energy barriers that affect the overall magnetic moment relaxation process and emerging as room temperature magnetic memory. The outcome of this study is attractive for the future development of the room temperature ferromagnetic oxide system to facilitate the integration of spintronic devices and understanding of their fundamental physics.

Superparamagnetic Magnetite Nanotubes Synthesized by Template-Assisted Sol–Gel Autocombustion

2020 ◽  
Vol 15 (11) ◽  
pp. 1381-1384
Author(s):  
Xinwei Zhang ◽  
Xuanyu Song ◽  
Huiyi Dong ◽  
Chao Zhang ◽  
Chunlei Wang
Keyword(s):  
Magnetic Measurements ◽  
Low Cost ◽  
Physical Property Measurement System ◽  
Sol Gel ◽  
Physical Property ◽  
Average Diameter ◽  
Blocking Temperature ◽  
Synthetic Process ◽  
Aspect Ratios ◽  
Potential Applications

Magnetite nanotubes with an average diameter of about 140 nm were synthesized by an AAO templateassisted sol–gel autocombustion method. The entire synthetic process is convenient, low-cost and nontoxic. The crystalline structure of the magnetite nanotubes was investigated by X-ray diffraction. From the diffraction pattern, we conclude that pure phase magnetite nanotubes were obtained. Tubular morphologies of the products were observed by transmission electron microscope. The as-prepared magnetite nanotubes have a high aspect ratios. The magnetic properties of the nanotubes were measured by a Physical Property Measurement System. The magnetic measurements indicate that the nanotubes have superparamagnetic characteristic at room temperature, and have ferromagnetic characteristic with a coercivity of about 518 Oe at 5 K. The blocking temperature TB of the nanotubes are measured to be 95 K. The as-prepared magnetite nanotubes may find potential applications in bio-medicine.

Sign in / Sign up

Export Citation Format

Share Document