Exploration of Novel Transition Metal Oxyarsenides
Lead Research Organisation:
University of Aberdeen
Department Name: Chemistry
Abstract
Spintronic materials can exhibit a large reduction in electronic resistivity upon application of a magnetic field, called magnetoresistance. Such materials are currently employed in magnetic sensors and magnetic memory devices such as computer hard disks. The discovery of giant magnetoresistance (GMR) in multilayers consisting of magnetic and nonmagnetic thin films was a major breakthrough, allowing the storage capacity of a hard disk to increase from 1 to 20 gigabits. GMR devices can exhibit a reduction in electronic resistivity of up to 50% upon application of a magnetic field. In recent years there has been intense study into the magnetic and electronic properties of manganite perovskites such as La1-xAxMnO3 (A = Ca, Sr, Ba) due to the observation of colossal magnetoresistance (CMR). The manganites are remarkable as they can exhibit a reduction in electronic resistivity of up to 99.9 % upon application of a magnetic field. As yet the large magnetic fields required to produce the CMR has limited its commercial implementation. An important research objective therefore is to discover new materials that exhibit CMR in low fields (<<1 T) at 290 K to be employed in spintronic devices for smaller, faster, cheaper and more efficient computing applications. It is therefore vital to synthesise and investigate novel CMR materials in order to gain greater understanding of different CMR mechanisms which can then be exploited in future CMR devices.
We have recently synthesised a new CMR material NdMnAsO1-xFx (x = 0.05 - 0.08) which surprisingly exhibits a reduction in electronic resistivity by 95% upon applying a magnetic field at low temperature, which is comparable to that observed in the CMR manganites. This is a new mechanism of CMR. The undoped compounds LnMnAsO (Ln = Nd, La) already exhibit a sizeable room temperature negative magnetoresistance (-MR; MR = -8% and -11% for Ln = Nd and La respectively in a 7 T magnetic field). We propose to improve the magnetoresistant properties of these fascinating Mn2+ oxyarsenides by exploring the effects of chemical substituents.
We will also synthesise and study the magnetotransport properties of novel Mn2+ oxyarsenides such as Sr2Mn2MAs2O2-xFx (M = Mn, Ni, Fe, Cu) in order to manipulate the CMR by enhancing magnetic coupling between Mn2+ and M2+ cations.
The magnetic and electronic properties of 3d transition metal oxyarsenides reported so far are exceptional. Alongside the observation of high temperature superconductivity in LnFeAsO1-xFx and CMR in NdMnAsO1-xFx, superconductivity has also been reported in LaNiAsO below 2.75 K whereas LnCoAsO is a ferromagnet below 66 K and 85 K for Ln = La and Nd respectively. We will investigate if novel superconducting and MR pathways are also present in 4d/5d transition metal oxyarsenide which have been relatively unexplored until now.
This work will not only be of great fundamental importance but may also have practical applications if it is possible to optimise the magnetoresistive properties.
We have recently synthesised a new CMR material NdMnAsO1-xFx (x = 0.05 - 0.08) which surprisingly exhibits a reduction in electronic resistivity by 95% upon applying a magnetic field at low temperature, which is comparable to that observed in the CMR manganites. This is a new mechanism of CMR. The undoped compounds LnMnAsO (Ln = Nd, La) already exhibit a sizeable room temperature negative magnetoresistance (-MR; MR = -8% and -11% for Ln = Nd and La respectively in a 7 T magnetic field). We propose to improve the magnetoresistant properties of these fascinating Mn2+ oxyarsenides by exploring the effects of chemical substituents.
We will also synthesise and study the magnetotransport properties of novel Mn2+ oxyarsenides such as Sr2Mn2MAs2O2-xFx (M = Mn, Ni, Fe, Cu) in order to manipulate the CMR by enhancing magnetic coupling between Mn2+ and M2+ cations.
The magnetic and electronic properties of 3d transition metal oxyarsenides reported so far are exceptional. Alongside the observation of high temperature superconductivity in LnFeAsO1-xFx and CMR in NdMnAsO1-xFx, superconductivity has also been reported in LaNiAsO below 2.75 K whereas LnCoAsO is a ferromagnet below 66 K and 85 K for Ln = La and Nd respectively. We will investigate if novel superconducting and MR pathways are also present in 4d/5d transition metal oxyarsenide which have been relatively unexplored until now.
This work will not only be of great fundamental importance but may also have practical applications if it is possible to optimise the magnetoresistive properties.
Planned Impact
This proposal primarily concerns the synthesis and study of novel Mn2+ oxyarsenides with important spintronic properties. Spintronic materials can exhibit a large reduction in electronic resistivity upon application of a magnetic field, termed magnetoresistance (MR). We have recently shown that the oxypnictide NdMnAsO1-xFx exhibits a sizeable room temperature magnetoresistance (x = 0) and colossal magnetoresistance (CMR) at low temperature (x = 0.05 - 0.08). Spintronic materials are used for magnetic memory in solid state devices and also in magnetic sensors. It is thought that future spintronic devices will capitalise on the CMR mechanism for smaller, faster, cheaper and more efficient "green" computing applications. We expect to synthesise new materials with improved performance which can be subsequently developed for spintronic applications. We will also investigate if novel MR and/or superconducting pathways are present in 4d/5d transition metal oxyarsenides which have been relatively unexplored until now.
This is blue skies research. Non-academic impact will be in the medium to long term, as described below.
Short Term (up to 3 years)
Short term non-academic impact will lie in the training of the postdoctoral researcher in the synthesis and characterisation of the oxyarsenide materials studied and in a variety of experimental measurement techniques (magneto(resistivity), magnetic susceptibility, neutron diffraction, thermogravimetric analysis).
Medium Term (3-5 years)
If significant low field magnetoresistance is found at ambient temperature in oxyarsenides then major industrial interest will arise. We will investigate opportunities of developing these applications.
Long Term (> 5 years)
In the long term superior spintronic materials will result in faster solid state devices which are smaller and hence will have lower power consumption and less cost. As such solid state devices (which range from supercomputers to mobile phones) will become more affordable which will impact on the quality of life of the general public.
The creation of new jobs to manufacture, distribute and sell new spintronic chips will also enhance the economic prosperity of the UK.
This is blue skies research. Non-academic impact will be in the medium to long term, as described below.
Short Term (up to 3 years)
Short term non-academic impact will lie in the training of the postdoctoral researcher in the synthesis and characterisation of the oxyarsenide materials studied and in a variety of experimental measurement techniques (magneto(resistivity), magnetic susceptibility, neutron diffraction, thermogravimetric analysis).
Medium Term (3-5 years)
If significant low field magnetoresistance is found at ambient temperature in oxyarsenides then major industrial interest will arise. We will investigate opportunities of developing these applications.
Long Term (> 5 years)
In the long term superior spintronic materials will result in faster solid state devices which are smaller and hence will have lower power consumption and less cost. As such solid state devices (which range from supercomputers to mobile phones) will become more affordable which will impact on the quality of life of the general public.
The creation of new jobs to manufacture, distribute and sell new spintronic chips will also enhance the economic prosperity of the UK.
Organisations
People |
ORCID iD |
Abbie Mclaughlin (Principal Investigator) |
Publications
Lawrence GB
(2020)
Electronic and Magnetic Properties of Cation Ordered Sr2Mn2.23Cr0.77As2O2.
in Inorganic chemistry
McCombie KS
(2018)
Relationship between the Crystal Structure and Electrical Properties of Oxide Ion Conducting Ba3W1.2Nb0.8O8.6.
in Inorganic chemistry
Wildman E
(2014)
Electronic and magnetic properties of Nd 1 - x Sr x MnAsO oxyarsenides
in Physical Review B
Wildman E
(2023)
Observation of an exotic insulator to insulator transition upon electron doping the Mott insulator CeMnAsO
in Nature Communications
Wildman EJ
(2015)
Absence of colossal magnetoresistance in the oxypnictide PrMnAsO0.95F0.05.
in Inorganic chemistry
Wildman EJ
(2016)
A Variable Temperature Synchrotron X-ray Diffraction Study of Colossal Magnetoresistant NdMnAsO0.95F0.05.
in Scientific reports
Wildman EJ
(2018)
The suppression of CMR in Nd(Mn1-xCox)AsO0.95F0.05.
in Dalton transactions (Cambridge, England : 2003)
Wildman EJ
(2015)
A high pressure neutron study of colossal magnetoresistant NdMnAsO(0.95)F(0.05).
in Journal of physics. Condensed matter : an Institute of Physics journal
Wildman EJ
(2015)
Absence of colossal magnetoresistance in the oxypnictide PrMnAsO0.95F0.05.
in Inorganic chemistry
Description | We have discovered that increasing electron doping (reducing the oxidation state of Mn) in NdMn1-xCoxAsO0.95F0.05 oxypnictides results in a change in magnetic state from antiferromagnetism to ferromagnetism. The colossal magnetoresistance (CMR) in NdMnAsO0.95F0.05 arises due to the unstable nature of the antiferromagnetic order of the Mn spins. The CMR is suppressed as the ferromagnetic state emerges with increasing electron doping. Preliminary results from high pressure resistivity experiments suggest a phase change at a pressure of 10 GPa. The resistivity decreases by 100 orders of magnitude. We will further investigate this with neutron diffraction. There is no evidence of CMR in PrMnAsO0.95F0.05. Instead a new magnetoresistance mechanism is observed at a structural transition at 32 K. We have shown that hole doping (increasing the Mn oxidation state) in Nd1-xSrxMnAsO (x = 0 - 0.1) also destroys the CMR. Instead the compound becomes metallic and positive magnetoresistance is observed at low temperature. Multiple magnetoresistance mechanisms are apparent in manganese oxypnictides. We have synthesised and investigated CeMnAsO1-xFx which appears to show an insulator insulator transition for x = 0.05 and 0.075. We have collected neutron diffraction data to understand the magnetic transitions and to see if there is any correlation between the magnetic and metal insulator transitions. The data show that there is no change in crystal or magnetic structure of CeMnAsO0.95F0.05 upon cooling. We believe that this is the first example of a many body localised state in a bulk electronic material. The CeMnAsO1-xFx phases investigated so far display all of the characteristics proposed for the MBL phase such as time dependence of the MBL transition temperature, strong sensitivity of the resistivity to the applied current and steps in the resistivity data at TMBL indicating a bistability caused by the overheating of the electrons. AC transport measurements have now shown that there are glassy dynamics around the transition and Seebeck measurements also show an anomalous response. We are now recording variable temperature Hall measurements to see if the carriers are less mobile below the transition. We have synthesised the new phase Sr2Mn2CrAs2O2. Two magnetic transitions are apparent below 150 K and 50 K. We will investigate the magnetic structure with neutron diffraction. |
Exploitation Route | These results will help physicists understand better the theory of CMR in Mn oxypnictides. This is a novel mechanism of CMR. We have shown that several magnetoresistance mechanisms are possible in Mn oxypnictide materials. It will help in the design of new materials. We have potentially discovered the first many body localised phase in a bulk electronic material. |
Sectors | Digital/Communication/Information Technologies (including Software),Education,Electronics,Energy |
Description | ILL studentship |
Amount | € 70,000 (EUR) |
Organisation | Institut Laue–Langevin |
Sector | Academic/University |
Country | France |
Start | 09/2018 |
End | 08/2024 |
Description | Many Body Localisation in the Solid State for Finite Temperature Quantum Computing |
Amount | £123,915 (GBP) |
Funding ID | EP/V047000/1 |
Organisation | Engineering and Physical Sciences Research Council (EPSRC) |
Sector | Public |
Country | United Kingdom |
Start | 01/2021 |
End | 01/2022 |
Title | (Magneto)resistivity data for CeMnAsO1-xFx (x = 0.025, 0.05 and 0.075) and NdMn1-xCoxAsO0.95F0.05 (x = 0.03 - 0.15) |
Description | Variable temperature magnetoresistivity data from 4 K - 300 K in magnetic fields of up to 7 T |
Type Of Material | Database/Collection of data |
Provided To Others? | No |
Impact | Still analysing the data. |
Title | A Variable Temperature Neutron Diffraction Study of NdMn1-xCoxAsO0.95F0.05 (x = 0 - 0.12) |
Description | Variable temperature neutron diffraction data recorded on GEM, ISIS from 5 K - 400 K. |
Type Of Material | Database/Collection of data |
Provided To Others? | No |
Impact | Still analysing the data |
Title | Magnetic data for CeMnAsO1-xFx (x = 0.025, 0.05 and 0.075) and NdMn1-xCoxAsO0.95F0.05 (x = 0.03 - 0.15) |
Description | Variable temperature magnetic susceptibility data from 4 K - 400 K recorded at the University of Edinburgh. |
Type Of Material | Database/Collection of data |
Provided To Others? | No |
Impact | Still analysing the data |
Title | Neutron diffraction Data of CeMnAsO0.95F0.05 |
Description | Variable temperature neutron diffraction data from 5 - 400 K showing changes in magnetic structure with temperature. |
Type Of Material | Database/Collection of data |
Year Produced | 2016 |
Provided To Others? | Yes |
Impact | Still analysing the data. |
Title | SQUID and electronic data for CeMnAsO1-xFx (x = 0.03 and 0.035) |
Description | SQUID and electronic data for CeMnAsO1-xFx (x = 0.03 and 0.035) |
Type Of Material | Database/Collection of data |
Year Produced | 2017 |
Provided To Others? | No |
Impact | Still analysing the data. |
URL | http://www.abdn.ac.uk/staffnet/research/pure-306.php |
Title | Variable Temperature Synchrotron Diffraction Data of NdMnAsO0.95F0.05 |
Description | Variable temperature synchrotron X-ray diffraction data on the CMR material NdMnAsO0.95F0.05 recorded from 4 - 300 K on beamline ID31, ESRF. |
Type Of Material | Database/Collection of data |
Provided To Others? | No |
Impact | Paper: E. J. Wildman and A. C. Mclaughlin, A Variable Temperature Synchrotron X-ray Diffraction Study of Colossal Magnetoresistant NdMnAsO0.95F0.05, Scientific Reports, 6, 20705 (2016). |
Title | Variable pressure neutron diffraction data of NdMnAsO0.95F0.05 |
Description | Variable pressure neutron diffraction data of NdMnAsO0.95F0.05 collected on the WISH diffractometer at ISIS at temperatures between 10 - 290 K and pressures of 0 - 4 GPa. |
Type Of Material | Database/Collection of data |
Provided To Others? | No |
Impact | We're still analysing the data. |
URL | http://www.abdn.ac.uk/staffnet/research/pure-306.php |
Title | X-ray diffraction data of LnMnAsO1-xFx and NdMn1-xCoxAsO1-xFx samples |
Description | A file containing all XRD data of phases synthesised for the first 1.5 years of the grant |
Type Of Material | Database/Collection of data |
Provided To Others? | No |
Impact | Too early at present |
Title | XRD and SQUID data for Sr2Mn2CrAs2O2 |
Description | Contains zero field cooled SQUID magnetometry data and X-ray diffraction from the new phase Sr2Mn2CrAs2O2. |
Type Of Material | Database/Collection of data |
Provided To Others? | No |
Impact | We are awaiting neutron data before publishing this. |
URL | http://www.abdn.ac.uk/staffnet/research/pure-306.php |
Description | Chemists exploring new material with 'next generation' computer hard drive possibilities |
Form Of Engagement Activity | A magazine, newsletter or online publication |
Part Of Official Scheme? | No |
Geographic Reach | Regional |
Primary Audience | Public/other audiences |
Results and Impact | Press release sent out on 27th January describing how the research could results in next generation' computer hard drives. This resulted in two interviews with two local radio stations. An attempt to uncover the 'holy grail' of a lossless energy source has inadvertently led to a study which could result in the next generation of high-speed, mass storage hard drives. I have had other magazines interested in the work who have since published our results around the world. This had widened the impact of our results so far. |
Year(s) Of Engagement Activity | 2014 |
Description | Magnets and superconductor experiments - school demonstration day |
Form Of Engagement Activity | A talk or presentation |
Part Of Official Scheme? | No |
Geographic Reach | Local |
Primary Audience | Schools |
Results and Impact | 120 primary school children attended a chemistry event at the University of Aberdeen. I performed a supercvonductivity and magnets experiment with them. Aided by colleagues Dr Peter Henderson, Dr Abbie Mclaughlin and Kieran McManus, 120 pupils were treated to an array of spectacular demonstrations on March 19 which included an array of controlled fireworks, screaming Jelly Babies, sudden colour changes, superconductivity, hydrogen explosions and making ice-cream in 17 seconds - all carried out in a controlled and safe environment. Too early to say |
Year(s) Of Engagement Activity | 2014 |
Description | Primary school chemistry day for British Science week - magnets and superconductor workshop |
Form Of Engagement Activity | Participation in an activity, workshop or similar |
Part Of Official Scheme? | No |
Geographic Reach | Local |
Primary Audience | Schools |
Results and Impact | 60 primary schools came to the chemistry department. I was one of the organisers of the event and introduced the primary 5 and 6 year old children to magnets. This included crushing up cornflakes to remove the iron content with a magnet, describing magnetic forces and giving a demonstration of superconductivity. |
Year(s) Of Engagement Activity | 2017 |
Description | School Visit to Demonstrate Magnetism and Superconductivity |
Form Of Engagement Activity | A talk or presentation |
Part Of Official Scheme? | No |
Geographic Reach | Local |
Primary Audience | Schools |
Results and Impact | I attended Albyn School, Aberdeen to demonstrate magnetism and superconductivity to primary 2 pupils. I attended Albyn school and gave the primary 2 children (40 pupils) a workshop on superconductivity and magnetism.This involved a brief talk, short experiments with magnets and a demonstration of magnetic levitation. Too early to say. |
Year(s) Of Engagement Activity | 2014 |
Description | School visit to give a talk about Ceramics |
Form Of Engagement Activity | A talk or presentation |
Part Of Official Scheme? | No |
Geographic Reach | Local |
Primary Audience | Media (as a channel to the public) |
Results and Impact | The PDRA on this research grant gave two separate talks about ceramics. One talk was to primary school children (P7) and the other was to secondary school children (U2). There was lots of questions afterwards. The primary school children were particularly engaged. |
Year(s) Of Engagement Activity | 2016 |
Description | Talk at the Solid state chemistry group christmas meeting |
Form Of Engagement Activity | A talk or presentation |
Part Of Official Scheme? | No |
Geographic Reach | National |
Primary Audience | Professional Practitioners |
Results and Impact | The talk sparked much discussion and questions afterwards. It was very well received. N/A |
Year(s) Of Engagement Activity | 2014 |
Description | Talk at the University of Reading |
Form Of Engagement Activity | A talk or presentation |
Part Of Official Scheme? | No |
Geographic Reach | Local |
Primary Audience | Professional Practitioners |
Results and Impact | The talk sparked lots of questions and discussion afterwards. There will hopefully be collaboration between research groups at the Universities of Aberdeen and Reading. |
Year(s) Of Engagement Activity | 2015 |
Description | Visit of a school pupil to perform his higher research project in chemistry at the University of Aberdeen |
Form Of Engagement Activity | Participation in an open day or visit at my research institution |
Part Of Official Scheme? | No |
Geographic Reach | Local |
Primary Audience | Schools |
Results and Impact | A primary school pupil worked in my laboratory for 2 days. His project involved the synthesis of the high temperature superconductor YBa2Cu3O7. He made and characterised this in my laboratory, I also demonstrated our X-ray diffractometers and we discussed my research in colossal magnetoresistant materials. |
Year(s) Of Engagement Activity | 2016 |