Friday,
March 29, our offices will be closed for the Easter weekend !!
24_03
It's St. Paddy's Day. A holiday for Irish Americans or all Americans?
I was reading an article on the importance of identifying as a Black American. The adjective “Black” suggests their shared struggles. It made me wonder if I should identify as “Irish American” rather than American?
The existence of Irish Americans is a testament to their ancestors surviving against the odds, but I wasn’t raised to be a victim. I was raised to have thick skin, stay out of trouble, pay my own way, and to know if I worked hard the sky was my limit. But shouldn’t I too embrace the struggles of my ancestors?
In the 17th century, the English cleansed Ireland of 616,000 people or about 43% of the population. After cleansing, their land was confiscated and tens of thousands were transported to the Thirteen Colonies as indentured servants.
In 1695, the British Penal Laws stripped the Irish of basic freedoms. In 1740, famine killed 400,000 Irish. Fewer would have died if British politicians had not enforced policies to exacerbate the famine. In 1776, the Irish owned 5% of Ireland’s land.
Graphic: Liberty Enlightening The World. British Library.
Wikimedia Commons.org. Public Domain.
Most early Irish Catholic immigrants to America came as indentured servants. The Atlantic voyages were perilous.
“Systematic villainy in the handling of human cargo was perhaps not so characteristic in this trade (Atlantic slave trade) as in the poverty-stricken white immigrants... I never saw an instance of cruelty in ten to twelve years in the [African] branch equal to the cruelty exercised on the poor Irish…They were to be delivered upon the cheapest terms possible.”
There was no welcome mat in America for the Irish. Hatred followed them across the Atlantic and so did the penal laws. In the 18th century, when non-Anglican Christians found acceptance in the Colonies, the Catholics did not. It was decreed that:
“forever hereafter there shall be liberty of conscience allowed in the worship of God to all Christians (except Papists).”
Between 1846 and 1855, 1.5 million Irish died of starvation. Historians note the British didn’t cause the 19th century potato blight, but they did cause the famine. The British thought Irish Catholics that refused to convert got what they deserved. The British saw the famine as heaven sent. Today, this is called ethnic cleansing or genocide.
Famine wasn’t enough punishment. About 500,000 starving Irish Catholics were evicted for not paying rent when crops failed. The stubborn Irish finally had enough. Nearly 2 million migrated to North America, and most to the United States. Some were paid to leave by the government and landlords. For the Irish, the decision was easy: emigrate or die. A lot died enroute. Many Irish were half dead when boarding ships for North America. The ships were called coffin ships, and on average, 20-30% died.
Researchers discover new kind of
magnetism
More than 200 materials could be “altermagnets,” predicted just a few years
ago
For thousands of years, people have been drawn to the apparent
magic of magnets. Ancient Greek philosophers believed dark rocks called
lodestones had souls because of their ability to move iron flakes.
Physicists now know that magnetic materials glean their power
from the behavior of the atoms inside them. But magnetism still holds secrets.
Researchers have recently found signs of a wholly new class of magnetism, one
with characteristics of each of the two conventional kinds, ferromagnetism and
antiferromagnetism.
More than 200 materials should exhibit the newfound
phenomenon, according to theoretical predictions, and physicists are closing in
on direct experimental evidence for it, which could lead to more efficient
electronic devices. Already they have found a handful of materials that seem to
exhibit this “fundamentally new type of magnetism,” says Paul McClarty, a
physicist at the Léon Brillouin Laboratory. “It’s expanding our understanding
of the ways that matter can work.”
Inside solid materials, atoms are surrounded by electrons
that all have a property called spin, which endows each atom with its own tiny
magnetic field. The total spin for each atom is represented by an arrow that
can point in different directions. In ferromagnets, all the spins inside the
material are aligned, resulting in a net magnetic field. In addition to
sticking photos to the fridge, ferromagnets are useful because their spins can
easily be flipped around by applying another magnetic field, creating distinct
states that can be used as computer memory. This technique birthed the emerging
technology of spintronics,
in which information is encoded via electron spin rather than charge.
In the 1930s, scientists realized it’s much more common for
the spins of neighboring atoms to point in opposite directions so their net
magnetization cancels out. Because the staggered arrangement is much more
stable than the uniform one, these antiferromagnets are nearly impossible to
magnetize with applied magnetic or electric fields. When French physicist Louis
Néel won a Nobel Prize in 1970 for his pioneering work on antiferromagnetism,
he described the phenomenon as “interesting but useless.” Nevertheless, the
concept has proved handy: During World War II, electric coils were used to make
ship hulls behave like antiferromagnets and evade magnet-seeking mines.
More recently, scientists have begun to devise strategies for
building spintronic devices out of antiferromagnets. Although their rigid spins
are harder to manipulate, they can in principle flip 1000 times faster than
those in ferromagnets, allowing for more energy efficient information storage
and processing.
A few years ago, Libor Šmejkal, a physicist at the Johannes
Gutenberg University of Mainz, was hunting for a possible antiferromagnetic
spintronic material. He stumbled across a compound called ruthenium dioxide
that seemed promising—but odd. His calculations
suggested it should have no net magnetization, like a normal antiferromagnet.
But he also predicted that when subjected to an electric current, the material
would behave like a ferromagnet: Magnetic forces in the material would deflect
the electrons in the current, leading to a strong voltage in the perpendicular direction.
In 2020, a team in China experimentally confirmed ruthenium
dioxide’s paradoxical properties.
The following year, Šmejkal and colleagues laid out a proposal
explaining how materials like ruthenium dioxide could be part ferromagnet and
part antiferromagnet. They called them altermagnets. In most materials,
electron spin arrows align with the orientation of their host atoms within the
crystal lattice. But in some materials, spin arrows can rotate independently of
the atoms, and Šmejkal and colleagues considered one in which every other atom
was rotated by 90° and its spin flipped by 180°.
Magnetism’s new twist
The properties of most magnetic materials depend on whether
each atom’s magnetic field—denoted by its spin—is pointing up (pink) or down
(blue). In altermagnets, the atoms and their spins rotate independently, giving
them properties of both ferromagnets and antiferromagnets.
Ferromagnetic Electron spins Atom Antiferromagnetic
Altermagnetic Rotated atom A. Mastin/Science
Altermagnets would combine the most prized features of
ferromagnets and antiferromagnets. With zero net magnetization, they are graced
with the stability and fast spin-flipping speeds of an antiferromagnet. But the
spins in an altermagnet, like those in a ferromagnet, can be readily ushered
into distinct up and down states, allowing for easier memory writing. “You can
have your cake and eat it, too,” says Jairo Sinova, another physicist in the
Mainz group. Whereas ferromagnetic spins are typically flipped with magnetic
fields, spins in an altermagnet could be manipulated by applying currents in
different directions.
Theorists were quick to accept Šmejkal’s description because
of its mathematical elegance, but many are surprised the phenomenon went
unnoticed for so long. “It’s one of those theoretical constructs which are
unquestionable,” says Igor Mazin, a physicist at George Mason University. “Yet
it has never been discussed before.”
More than 200 materials are predicted to be
altermagnetic—more than double the number of known ferromagnetic materials.
Researchers are now beginning to look for the property by shining laser light
on a material to coax it to eject electrons. By measuring the properties of
those electrons, scientists can look for a hallmark of altermagnetism: energy
levels that fall within two distinct bands, reflecting both spin-up and
spin-down electrons. (Antiferromagnets also have spin-up and spin-down
electrons, but they sit at the same energy levels.)
Last month, a team in South Korea found the predicted
split in electron energies in the material manganese telluride. Two
additional recent studies
identify similar signals in manganese telluride and ruthenium dioxide, and also
attempt to tie the energy bands to specific spin polarities. “Crystal-clear
proof is really hard to achieve experimentally,” says Suyoung Lee, a Ph.D.
student at Seoul National University who led one of the latest studies. “But I
would say that we now have sufficient experimental evidence … that altermagnetism
is really a thing.”
McClarty says the new experiments are “consistent with
altermagnetism,” but only reveal the spin behavior through a slice of the
material’s magnetic landscape. Until experimentalists capture the behavior
across an entire 3D structure, “I wouldn’t hang up my coat,” he says. Also,
before altermagnets can be exploited in electronic devices, scientists must
learn to synthesize materials that have a consistent altermagnetic orientation
rather than a patchwork of shifting configurations.
Mazin says confirmation of materials’ altermagnetic makeup is
all but certain. “There’s no way in nature that they wouldn’t be,” he says. He
sees the verification effort akin to “an experiment that proves two times two
is four.”
But for Lee, the hunt promises other payoffs: an opportunity
to explore emergent complex phenomena that may lead to practical applications.
“I think this is the starting point for a whole new field of altermagnetism,”
she says. “I am happy to be part of it.”
Zack Savitsky - author
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OUR OFFICES WILL BE CLOSED ON DECEMBER 25 AND 26, AND JANUARY 1 AND 2. HAPPY HOLIDAYS!!
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